winter 1998 gems & gemology - gia · pdf fileof gia’s “make grade”...

243 LETTERS

FEATURE ARTICLES246 Characterizing Natural-Color Type IIb Blue Diamonds

John M. King, Thomas M. Moses, James E. Shigley, Christopher M. Welbourn, Simon C. Lawson, and Martin Cooper

270 Fingerprinting of Two Diamonds Cut from the Same Rough

Ichiro Sunagawa, Toshikazu Yasuda, and Hideaki Fukushima

NOTES AND NEW TECHNIQUES281 Barite Inclusions in Fluorite

John I. Koivula and Shane Elen

REGULAR FEATURES284 Gem Trade Lab Notes290 Gem News303 Book Reviews306 Gemological Abstracts314 1998 Index

ABOUT THE COVER: Blue diamonds are among the rarest and most highly valued ofgemstones. The lead article in this issue examines the history, sources, and gemologicalcharacteristics of these diamonds, as well as their distinctive color appearance. Rela-tionships between their color, clarity, and other properties were derived from hundreds of samples—including such famous blue diamonds as the Hope and the Blue Heart (orUnzue Blue)—that were studied at the GIA Gem Trade Laboratory over the past severalyears. The diamonds shown here range from 0.69 to 2.03 ct.Photo © Harold & Erica Van Pelt––Photographers, Los Angeles, California.

Color separations for Gems & Gemology are by Pacific Color, Carlsbad, California.Printing is by Fry Communications, Inc., Mechanicsburg, Pennsylvania.

© 1998 Gemological Institute of America All rights reserved. ISSN 0016-626X

T A B L E O F C O N T E N T S

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pg. 298

pg. 281

pg. 271

WINTER 1998 VOLUME 34 NO. 4

Letters GEMS & GEMOLOGY Winter 1998 243

GIA “Cut” Report Flawed?

The long-awaited GIA report on the ray-tracing analysisof round brilliant diamonds appeared in the Fall 1998Gems & Gemology (“Modeling the Appearance of theRound Brilliant Cut Diamond: An Analysis of Brilliance,”by T. S. Hemphill et al., pp. 158–183). The writer initiallysaw this article as an opportunity to qualitatively validatehis own SAS2000 two-dimensional ray-tracing facility,but soon realized that this report on the brilliance aspectof cut grade analysis, based on GIA’s weighted lightreturn (WLR) metric, contains what appears to be anunintentional fatal flaw in its design: The hemisphericallighting model chosen by GIA for this study is not anunbiased benign source, and as a result it probably invali-dates any conclusions presented in the article. The use ofany comparisons in the G&G article should be strictlyavoided, as the illumination model chosen apparently(based on limited SAS2000 two-dimensional analyses)weighs the results toward favoring shallower crownangles and possibly larger tables.

A scientific perturbation analysis such as thatattempted in GIA’s report is intended to show the effecton some output parameter (such as GIA’s defined WLR)as a function of a change in a given parameter or combi-nation of parameters. The model chosen by GIA wasapparently intended to present a uniformly (diffuse) dis-tributed set of input ray incident angles to the modeleddiamond, each emanating from the hemisphere’s internalsurface. The amount of light entering the diamond (thatwhich can potentially contribute to WLR) is dependenton the angle of incidence, and the researchers sought auniform distribution of this angle of incidence.

Figure 1A shows a ray incident on the table (RO), orig-inating from the hemisphere, with angle of incidence idefined by ROP. For the table, any ray such as ROP can havean angle of incidence bounded by the 90° angles defined byPOA and POB, where PO is a normal to the table.

For any other crown facet, such as the crown mainshown in figure 1B, rays originating from the hemisphere,such as R’O’ (defined by the angle R’O’P’), are limited asto angle of incidence i’, by the angles defined by P’O’A’and P’O’B’, where P’O’A’ is less than the 90° angledefined by P’O’B’. P’O’ is a normal to the crown mainshown. With this model, the allowed angular inputs forany facet below the table change as the facet anglechanges—hardly the uniform, unchanging, angular distri-

bution applied to the table facet. Theoretically at least,the allowed angular range within a given point in a partic-ular crown facet also changes, the magnitude of thechange dependent on the radius chosen for the illuminat-ing hemisphere. The angle defined by P’O’A’ is, in thelimit defined by an infinite hemispherical radius, equal to90° minus the crown angle. Likewise, in GIA’s three-dimensional model, the star and break facets will eachhave similarly defined angular ranges, with an individualangular cutoff on one side of the range.

What does all this mean? To this writer, it mandatesan immediate retraction of the G&G article by GIA and arepublication of results with a corrected model.

GIA should also, to eliminate what is a perceived biasin their report, include in an amended table 3 comparisonof GIA’s “Make Grade” system, which is taught in theirown educational courses, regardless of the results shown:good, bad, or indifferent.

Martin HaskeAdamas Gemological Laboratory

Boston, Massachusetts

Authors’ Reply

We thank Mr. Haske for drawing attention to theseissues. We believe that many of his concerns stem fromthe difference between two-dimensional and three-dimen-sional analysis of the appearance of a diamond.

Mr. Haske states that he examined our results for thepurpose of comparison with his own two-dimensional(SAS2000) analytical system. He evidently suspects thatour diffuse hemispherical illumination condition is the

Figure 1. GIA’s hemispherical input model.

244 Letters GEMS & GEMOLOGY Winter 1998

likely cause of the apparent disagreement between hisanalyses and our results, rather than the difference in thenumber of dimensions used in the two approaches. Wechose this lighting condition because we believe that itrepresents the best average of the many ambient lightconditions in which diamonds are viewed. A diffusehemisphere of light at infinite distance is exactly that:Light rays of all angles emanate from all points on theinside of this hemisphere. We sought a uniform distribu-tion of light with regard to the diamond as a whole, notover each facet independent of the other facets.

The “apparent flaw” Mr. Haske shows in his diagramis in fact the expected result of illuminating the diamondfrom above the girdle with a hemispherical source. Likeall three-dimensional objects, a round brilliant diamondthrows some small shadow on itself, and our model cap-tures this aspect of real diamonds. All of the crown facets,including the table, are partly in the shadow of otherfacets (e.g., for rays originating between points B’ and X inhis figure 1B, the far bezel is in the “shadow” of the tableand near bezel facet). One of the differences between a 2Dmodel and a 3D model is the extent of this shadowing. Inthree dimensions, light rays coming from in front andbehind impinge the particular “crown main” (bezel) facetat many of the angles that appear blocked in a two-dimen-sional view, for which the light source is an arc ratherthan a hemisphere. We know of no publication in the sci-entific literature on SAS2000 analyses of diamond cutappearance, and so do not know what other differencesthere might be between the two approaches, or whethersuch differences would be relevant.

Note also that the paths of some rays through the dia-mond cannot be represented in two dimensions, as was

shown in figure A-2 of the original paper (p. 167). Giventhe different effects from two-dimensional and three-dimensional models, we do not believe Mr. Haske’s geo-metrical argument applies to (three-dimensional) round,brilliant-cut diamonds.

Mr. Haske also writes that we attempted a “perturba-tion analysis.” In fact, we did no such thing. Perturbationanalysis is used to evaluate a mathematical function, tofind out whether any particular point (in however manyparameter dimensions) is a local maximum (a bump), alocal minimum (a divot), or something else (such as a sad-dle point, which is a peak in one direction but a valley inanother). It works by evaluating that function at thatpoint, and then examining how the value changes as youmove slightly away from that point. Although this tech-nique could be used to find the exact location of the vari-ous local maxima in the WLR surfaces, we did not thinkthis was necessary at this time.

Finally, Mr. Haske refers to a “Make Grade” systemtaught in the GIA courses. The GIA Diamond GradingCourse (see, e.g., Assignment 9, 1994, pp. 15–17, 20–21)describes four general classes of cut as a teaching tool, butnever proposes that they be used as a grading system.Thus, it was not appropriate to include them in table 3.The approximate values of WLR across the range of pro-portions described by these classes can be readily seenfrom the data given in the article.

In conclusion, we stand behind our study as publishedin Gems & Gemology, and do not feel that any correctionis necessary.

T. Scott Hemphill, Ilene M. Reinitz,Mary L. Johnson, and James E. Shigley

Gemological Institute of America

246 Blue Diamonds GEMS & GEMOLOGY Winter 1998

ecause of their great beauty and rarity, blue dia-monds are both intriguing and highly valued (fig-ure 1). Such important historic diamonds as the

Hope, the Blue Heart (also called the Unzue or Eugénie Blue),and the Idol’s Eye have greatly added to the fascination andmystery surrounding blue diamonds throughout history.

In recent years, auction sales have also placed blue dia-monds in the forefront of industry interest. The currentrecord per-carat price paid for a blue diamond at auction,$569,000, was set inNovember 1995, for a 4.37 ct FancyDeepblue oval shape which sold at Christie’s Geneva. Only threediamonds have sold at auction for higher per-carat prices;indeed, of the 10 highest per-carat prices paid for colored dia-monds at auction, six have been for blue diamonds (WorldDiamond Industry Directory&Yearbook, 1997/98, p. 56).

Even with their high profile, blue diamonds have longbeen considered among the rarest of gems (Federman, 1989,1998). The De Beers Polished Division, in their publishedcompilation Important Diamond Auction Results 1997,noted only 18 blue diamonds offered for sale that year at theauction houses of Christie’s, Sotheby’s, and Phillips (in con-trast to 143 predominantly yellow diamonds noted for thesame period). Of the numerous colored diamonds submittedfor grading reports to the GIA Gem Trade Laboratory (GIAGTL) during the first half of 1998, only 0.3% were describedas predominantly blue. Although such diamonds are muchsought after, dealers indicate that only a couple of new bluediamonds come to their attention during the course of ayear (K. Ayvazian and I. Gol, pers. comm., 1998). This obser-vation is consistent with the current mining recovery rate.Of all the De Beers South African rough production, there ison average “only one significant blue” mined per year.When they occur, such finds are said “to cause excitementalong the chain from the discovery at the mine to the sort-ing” (M. Semple, pers. comm., 1998).

In GIA GTL’s color grading of colored diamonds, there

CHARACTERIZING NATURAL-COLORTYPE IIB BLUE DIAMONDS

By John M. King, Thomas M. Moses, James E. Shigley, Christopher M. Welbourn,Simon C. Lawson, and Martin Cooper

Although rarely encountered, blue dia-monds are among the most famous, andmost distinctive, of fine gemstones. To bet-ter understand these unique gems, morethan 400 were studied at the GIA GemTrade Laboratory over several years toreveal additional information about therelationships between their color, clarity,and other gemological properties. The over-whelming majority of natural-color bluediamonds are type IIb. The color appear-ance varies widely from light to dark, butthere is a limited range of color saturation.As a result, color appearance betweenneighboring GIA GTL color grades can besubtle. Of the blue diamonds examined atGIA GTL, few had any solid inclusions.Nevertheless, internal features such asgraining and color zoning can make theprocessing of these diamonds a challenge.

B

ABOUT THE AUTHORS

Mr. King is laboratory projects officer, and Mr.Moses is vice president of Identification Services,at the GIA Gem Trade Laboratory in New York.Dr. Shigley is director of research at GIA inCarlsbad, California. Dr. Welbourn is head ofPhysics, Dr. Lawson is a research scientist in thePhysics Department, and Mr. Cooper is researchdirector, at De Beers DTC Research Centre,Maidenhead, United Kingdom.

Please see acknowledgments at end of article.

This is a Carat Achievement article. Participatingmembers of GIA Alumni & Associates receivetwo carat points for reading the article.

Gems & Gemology, Vol. 34, No. 4, pp. 246–268© 1998 Gemological Institute of America

Carat Points

Blue Diamonds GEMS & GEMOLOGY Winter 1998 247

are other natural colors that are more rarely encoun-tered than blue (such as purple or red). However, itis the combination of relative rarity (although thenumbers are small, they are sufficient to enable arecognized market to be established), high value,and trade enthusiasm that makes it critical toexpand our knowledge of blue diamonds. In particu-lar, precisely because blue diamonds are so rare, fewdealers understand their full range of color appear-ances. This is important to accurately assess therelationship of one blue diamond to another. As isthe case with other aspects of diamond valuation,subtle differences in color appearance (reflected indifferences in grading terminology)* can result inlarge differences in value. Therefore, understandingand consistently describing color in blue diamondsis critical.

To this end, GIA GTL and GIA Research havebeen compiling for several years (as well as drawing

on the Laboratory’s more than 40 years of reportingon these stones) information based on a significantquantity of blue diamonds they have graded and/orotherwise documented. This study represents thelargest number of blue gem diamonds ever exam-ined by a single organization, including some of themost famous diamonds known.

Following a discussion of the history of blue dia-monds and a mention of some of the main localitieswhere they are found, the present article reports onthe relationship of the various color appearances ofblue diamonds, as reflected in their GIA GTL colorgrades, to their other gemological properties.

Figure 1. Blue diamonds areamong the most highly

prized objects in contempo-rary society. The connoisseurof such stones appreciates the

subtle differences andnuances of color. Shown here

are a range of appearancesfrom the strongly colored

heart shape in the ring to thegray-blue marquise shape atthe upper left. The diamondsrange from 0.48 ct to 2.01 ct;the 1.04 ct blue diamond in

the ring is surrounded byapproximately 2 carats ofnear-colorless diamonds.Loose stones courtesy of

Rima Investors Corp.; thering is courtesy of Martin

Kirschenbaum Trading, Inc.Composite photo © Harold &

Erica Van Pelt.

*Note that this article contains a number of photos illustrat-ing subtle distinctions in color. Because of the inherent diffi-culties of controlling color in printing (as well as the insta-bility of inks over time), the color in an illustration may dif-fer from the actual color of the diamond.


BACKGROUNDHistory and Geographic Origin. Historically, bluediamonds have been recovered from several locali-ties. Early accounts cite the Kollur mine (and possi-bly other mines) along the Krishna River valley nearGolconda, in the Indian state of Hyderabad (nowcalled Andhra Pradesh; Scalisi and Cook, 1983).This region was described by noted French travelerand gem dealer Jean-Baptiste Tavernier (1676). Overthe course of almost 40 years (1631–1668),Tavernier made six journeys from Europe to India.At that time, India was the source of almost all gemdiamonds. During these visits, Tavernier saw manyspectacular rough diamonds, a number of which hepurchased and brought back to Europe.

Tavernier is widely believed to have acquiredone of the world’s most famous diamond crystals,the 112.5 ct stone that became known as theTavernier Blue, in India in 1642 (Tillander, 1975).

He sold this rough diamond to Louis XIV of Francein 1669, who had the diamond cut into a triangularshape of 67.12 ct (possibly with additional smallercut stones). In 1792, during the French Revolution,this and other diamonds were stolen from the col-lection of the French Crown Jewels housed in theGarde Meuble palace. It is believed that, to avoiddetection, subsequent owners had the TavernierBlue recut twice, ultimately to a weight of 45.52 ct,before Henry Philip Hope purchased it in 1830 (fig-ure 2). Currently on exhibit in the Harry Winstongallery at the Smithsonian Institution inWashington, DC, the Hope diamond is seen bymore than four million museum visitors each year(J. E. Post, pers. comm., 1998).

The 70.21 ct Idol’s Eye is also reported to havebeen found in the Golconda district in the early17th century. Like the Hope, it is a classic exampleof a diamond with a history surrounded by mythsand legends (Krashes, 1993). It was claimed to havebeen set in the eye of an idol in the Temple ofBenghazi, rumored to have been seized from itsoriginal owner for payment of debts, and disap-peared for 300 years before resurfacing. This lightblue diamond was rediscovered in the possession ofAbdul Hamid II (1842–1918) in 1906, who becamethe 34th Ottoman Sultan.

A number of other important blue diamondshave published histories (see, for example, Balfour,1997) and specific names that have lasted for manyyears. Table 1 presents a list of some of thesenotable blue diamonds, with their weights, colordescriptions, cut shapes, and the most recent yearthat individual stones were examined by GIA staffmembers.

Today, there is little production at the Indianmines. The Premier mine in South Africa is nowconsidered the most significant source of the bluediamonds entering the market (Federman, 1989; G.Penny, pers. comm., 1998).

The Premier Mine. Discovered in 1903, the Premiermine was initially worked by open-pit methods (fig-ure 3); in 1905, it yielded the largest rough diamondever found, the 3,106 ct Cullinan. In celebration ofthe gift of this diamond to King Edward VII ofEngland, Thomas Cullinan, then chairman of thePremier mine, presented his wife with a necklacethat contained several blue diamonds, including a2.60 ct center stone (illustrated in Janse, 1995, p. 240).

The open-pit operations were closed in 1932, butDe Beers reopened the Premier in 1946 as an under-

Figure 2. The excitement generated by the his-toric 45.52 ct Hope diamond, now on display

at the Smithsonian Institution, is due asmuch to its Fancy Deep color as to the dra-

matic events associated with its various own-ers. Photo © Harold & Erica Van Pelt.


ground mine, with full production attained in 1949.Underground operations continue to the presenttime (figure 4).

Since mining began at the Premier in 1903, 278million tons of ore have been processed and 90.5million carats of gem and industrial diamondsrecovered. Current production is approximately 1.6million carats per year. The yield is 50 carats per100 tons of ore, or approximately 0.50 ct per ton. Ofthis production, diamonds with any evidence ofblue color (but that would not necessarily colorgrade as blue once cut and polished) represent lessthan 0.1% (H. Gastrow, pers. comm., 1998). ThePremier mine is well known as a source not only ofblue diamonds, but also of large, colorless diamondcrystals. Indeed, it is the three or four blue and/orcolorless “specials” recovered each year that makethe Premier mine a viable operation (G. Penny, pers.comm., 1998). To date, there is no known correla-

tion between the geologic conditions of the hostrock and the type or color of diamond recoveredfrom the Premier mine or elsewhere; the recovery ofblue diamonds is random and very sporadic (D. E.Bush, pers. comm., 1998).

Other South African mines that have producedblue diamonds include the Jagersfontein andKoffiefontein (both near Kimberley); the Bellsbankmine near Barkly West; and the Helem mine atSwartsruggens. Very rarely, blue diamonds havebeen found in alluvial deposits at Lichtenburg in theWestern Transvaal. Guinea, in western Africa, isalso known to have produced blue diamonds(Webster, 1994). Historically, central Africa hasbeen rumored to be a source of blue diamonds, espe-cially Sierra Leone for lighter blues (A. Arslanian,pers. comm., 1997). Outside of Africa, blue dia-monds have been reported from Kalimantan on theisland of Borneo in Indonesia (Spencer et al., 1988),

TABLE 1. Notable blue diamonds.a

Date of the most recentName Weight Color descriptionb Shape GIA Gem Trade Laboratory

(carats) report/examination

Brazilia 176.2 “light blue” Rough nee

Idol’s Eye 70.21 Light blue Modified triangle 1995Mouawad Blue 49.92 Fancy Dark blue Pear 1984Copenhagen Blue 45.85 “blue” Emerald neHopec 45.52 Fancy Deep grayish blue Cushion 1996Tereschenko 42.92 “blue” Pear neGraff Imperial Blue 39.31 Fancy Light blue Pear 1984Wittlesbach 35.50 “blue” Oval neSultan of Morocco 35.27 “bluish gray” Cushion neNorth Star 32.41 “blue” Pear neBlue Heart (Unzue Blue)c 30.62 Fancy Deep blue Heart 1997Blue Lili 30.06 Fancy blue Cushion 1980Transvaal Blue 25.00 “blue” Pear neHoweson 24 “blue” nrd neBegum Bluec 13.78 Fancy Deep blue Heart 1995Brunswick Blue 13.75 “blue” Pear neGraff Blue 6.19 Fancy Dark blue Round 1990Marie Antoinette Blue 5.46 “blue” Heart neCullinan Blue necklace (center stone) 2.60 “blue” Cushion 1993

a Information obtained from GIA GTL reports or examination of individual diamonds (as indicated by a date given in the lastcolumn), as well as from the GIA Diamond Dictionary (1993), Christie’s Jewellery Review 1995 (1996), and Balfour (1997).

bColor descriptions for diamonds graded by GIA GTL (i.e., those that are not set off by quotation marks) represent the colorgrading terminology that prevailed at that time. Modifications to the GIA GTL colored diamond color grading systemand its nomenclature were introduced in 1995.

c Diamonds that were examined as part of this study.dnr = not recorded.e ne = not examined.


from several regions in Brazil (Cassedanne, 1989),and from areas of Guyana and Venezuela (Webster,1994; also see Bruton, 1978).

Past Studies of Blue Diamonds. Although blue dia-monds have been known for centuries, only rela-tively recently have they become the subject of sci-entific study (see Box A). One of the results of suchstudy was the identification of most blue diamondsas type IIb. Historically, the classification of dia-mond into two types has been determined by thedifferences in the diamond’s transparency to ultravi-olet (UV) radiation and in its infrared spectra(Robertson et al., 1934). In a type I diamond, UV

radiation is not transmitted substantially belowabout 300 nm, whereas type II diamonds transmitUV down to 230 nm. Because only simple equip-ment is needed, UV transparency is commonly usedby gemologists to separate diamonds into these twobasic categories.

The region of the infrared spectrum that is usedto determine type (1000–1400 cm−1) is referred to asthe “nitrogen” region. Type I diamonds (whichcomprise most gem-quality stones) contain signifi-cant amounts of nitrogen, whereas type II diamondsdo not. (For a discussion of diamond types, seeFritsch and Scarratt, 1992.) A further distinctionwithin the type II classification was made in 1952(see Box A). In the 1950s, irradiation and annealingof “off-color” diamonds began to be used commer-cially for the color treatment of gem diamonds,some of which turned blue (see, e.g., Schulke, 1962).As a result, concerns quickly arose in the tradeabout how a treated-color blue diamond could beidentified by jewelers. During this period, J. F. H.Custers reported that natural-color blue diamondsdisplay electrical conductivity with an efficiencycapacity somewhere between that of a conductor(such as copper) and a nonconductor (such as glassor typical near-colorless diamonds); this capacity isreferred to as semi-conductivity (Custers, 1954,1955). Because of their electrical conductivity andtheir lack of substantial nitrogen, and because theyexhibit a mid-infrared spectrum that is quite differ-ent from the spectra of other diamonds, these semi-conducting blue diamonds were designated as typeIIb (again, see Box A).

On the basis of this electrical conductivity, earlycooperation between GIA and De Beers resulted in thedevelopment of a simple conductometer in 1959(Crowningshield, 1959; Benson, 1959). This proved veryeffective in distinguishing natural-color type IIb bluediamonds from treated-color blues of other diamondtypes (Custers andDyer, 1954;Custers et al., 1960).

Recently, gemological researchers have recog-nized the existence of two other categories of natu-ral-color blue diamonds (figure 5): (1) blue to green-blue type Ia or IIa diamonds that owe their color tonatural radiation exposure (Fritsch and Shigley,1991); and (2) gray-blue to gray-violet type Ia dia-monds, in which the color is associated with thepresence of hydrogen (Fritsch and Scarratt, 1992).These other two groups of natural-color blue dia-monds are not electrically conductive, and theirgemological properties differ from those of type IIbdiamonds. In our experience, these two categories of

Figure 3. Opened in 1903, the Premier mine inSouth Africa is considered the principal producer of

blue diamonds today. Note the original open-pitmine in the background and the modern processingplant in the foreground. Photo courtesy of De Beers.


diamonds are rarely described as simply “blue”(without a modifier) in the GIA GTL grading sys-tem. Those non-IIb diamonds that are described as“blue” represent a miniscule number of the bluediamonds examined in GIA GTL. For these reasons,they are not part of this study. In addition, becausethe overwhelming majority of diamonds describedas blue by GIA GTL are natural-color type IIb, thisarticle deals only briefly with their separation fromtreated-color diamonds. (The latter are typicallygreen-blue, not blue, and are never electrically con-ductive). Likewise, although gem-quality synthetictype IIb blue diamonds have been produced experi-mentally (Crowningshield, 1971), they are not com-mercially available. Therefore, they are not a signifi-cant part of this study either.

Some information on blue diamonds is present-ed in books by, for example, Liddicoat (1987, p. 230),Webster (1994), and Hofer (1998). A brief summaryof the gemological properties of natural-color typeIIb blue diamonds was presented as part of a natu-ral/synthetic diamond identification chart byShigley et al. (1995). To date, however, we know ofno previous systematic study in which the gemo-logical characteristics of a large number of blue dia-monds have been documented.

MATERIALS AND METHODSSamples. Over the course of the past 40 years, andin particular during the 1990s, staff members at theGIA Gem Trade Laboratory and GIA Research haveexamined hundreds of natural-color type IIb bluediamonds. For the present study, we gathered datafrom a representative sample of more than 400 ofthese diamonds, each of which was described as pre-dominantly blue (i.e., blue, grayish blue, and gray-blue), to explore their color relationships with eachother and with their gemological properties. Thepolished diamonds ranged from 0.07 to 45.52 ct (65weighed more than 5 ct). Based on their infraredspectra and/or electrical conductivity, the diamondsin this study were all type IIb. Because of time con-straints or other restrictions, it was not possible togather all data on all of the blue diamonds includedin this study. Some data (such as duration of phos-phorescence) are not typically recorded in thecourse of routine gemological testing, as it is theabsence or presence of the phenomenon that ismost relevant. In specific cases, some tests couldnot be performed due to the conditions under whichwe were required to grade. For example, we typical-ly cannot perform comprehensive testing (e.g., for

the Hope diamond) when the grading must be doneoff the GIA GTL premises. Also, because GIA GTLoffers different reporting services for colored dia-monds, different data are captured for differentstones. For example, laboratory clients do notrequest a clarity grading on all colored diamonds.Consequently, we collected data on random subsetsof blue diamonds for some properties (e.g., durationof phosphorescence). The number of stones exam-ined for some key characteristics are listed in table2; other sample numbers are given in the Resultssection.

Grading and Testing Methods. We used standardGIA GTL colored diamond color-grading methodol-ogy to determine the color descriptions and rela-

Figure 4. Since 1946, the Premier mine has beenoperated underground. The occasional recovery ofblue diamonds helps make the expensive under-ground mining viable. Photo courtesy of De Beers.


Wavelength (nm)

Wavenumber (cm-1)

Photon energy (eV)

Ad

sorp

tio

nco

effic

ient

(cm

-1)

Natural type IIb

Natural type IIa

2928

cm-1

2985 cm-1

2802 cm-1

2455

cm-1

1332

cm-1

Ultraviolet Visible Infrared

250 300 400 600 1000 2000 2500 3333 5000 10,000

10,00016,70025,00033,33340,000 4000 3000 2000 1000

6 5 4 3 2 1 0.7 0.6 0.5 0.4 0.3 0.2 0.10

5

10

15

20

25

5000

The classification “type IIb” was suggested by Custers(1952) for type II diamonds that displayed phosphores-cence after excitation with short-wave UV radiation.He noted that these diamonds also showed higher elec-trical conductivity than usual. The diamonds studiedin this initial work were described as “water white” orlight brown. However, in a note, Custers mentionedthat similar characteristics had been seen in a diamondthat was “a diluted bluish color.” Further work byCusters (1954) showed that blue diamonds did indeedconsistently exhibit high electrical conductivity andphosphorescence.

It was initially believed that the impurity responsi-ble for the characteristic features of type IIb diamondswas aluminum (Austin and Wolfe, 1956; Dean et al.,1965; Lightowlers and Collins, 1966). However, whenWentorf and Bovenkerk (1962) produced synthetic dia-monds doped with boron, they found that depth ofblue color increased with boron content. They pro-posed that boron was responsible for the characteristicfeatures of type IIb diamonds. Subsequently, Collinsand Williams (1971) and Chrenko (1973) found thataluminum concentrations could not account for typeIIb characteristics in diamonds, whereas Chrenko(1973) and Lightowlers and Collins (1976) showed thatthere was a good correlation between boron concentra-

tion and electrical conductivity in diamonds.Electrical measurements (Leivo and Smoluchowski,

1955; Custers, 1955; Brophy, 1955; Austin and Wolfe,1956; Dyer and Wedepohl, 1956; Wedepohl, 1956;Collins and Williams, 1971) showed that type IIb dia-monds behave as semiconductors: The electrical conduc-tivity increaseswith increasing temperature. Thesemea-surements also revealed that the conductivity is p-type.In p-type semiconductors, electrical current is carried bypositively charged “holes,” whereas in n-type semicon-ductors it is carried by negatively charged electrons.

A “hole” is what is left behind when an electron ismissing from the normal bonding structure of a semi-conductor. If an electron moves in to fill the hole, thenanother hole is left at that electron’s original position.Although it is actually the negatively charged electronthat has moved, the effect is the same as if a positivelycharged hole had moved in the opposite direction.Holes result when impurities known as acceptors arepresent. An acceptor can “accept” an electron from thebonding structure of the semiconductor, leaving a holebehind. In diamonds, boron acts as an acceptor; aboron atom contributes only three electrons to thebonding structure of the diamond crystal, whereas acarbon atom contributes four electrons (thus there is adeficiency of one electron per boron atom).

Figure A-1. The UV-Vis-IR spectrum of a natural type IIb diamond is shown in blue and, for comparison, thatof a natural type IIa diamond is in red. The IR absorption of the type IIb below 1332 cm−1 results from latticevibrations induced by boron impurities. The bands at 2455, 2802, and 2928 cm−1 are due to transitions of holesfrom the ground state to excited states of the boron acceptors. The absorption starting at 2985 cm−1 and contin-uing with decreasing intensity into the visible range corresponds to electrons being excited from the valenceband to neutral acceptors. The fact that this absorption extends into the visible part of the spectrum, anddecreases in intensity from the red end toward the blue end, gives rise to the blue color in type IIb diamonds.

BOX A: THE PHYSICS OF BLUE TYPE IIB SEMICONDUCTING DIAMONDS


Analysis of the electrical measurements citedabove implied that not all of the boron acceptors pre-sent in diamonds contribute to the semiconductingbehavior. Even in type II diamonds, there are sufficientconcentrations of nitrogen (although typically less than0.1 ppm) to influence the electrical behavior. Nitrogen,which contributes five electrons to the bonding struc-ture of a diamond crystal, acts as an electron donor.They donate electrons to boron acceptors, whichbecome permanently ionized. These acceptors are saidto be “compensated” by an electron from the nitrogen.Only the uncompensated acceptors contribute to semi-conductivity, so the strength of this behavior dependson the difference between the boron and nitrogen con-centrations, not on boron concentration alone.

The blue color of type IIb diamonds results fromthe decreasing edge of a region of absorption that iscentered in the infrared and extends into the visibleregion of the spectrum. In addition to the intrinsicabsorption exhibited by all diamonds, the infraredspectrum of type IIb diamonds, when measured atroom temperature, has a series of bands located at2455, 2802, and 2928 cm−1 (figure A-1). These bandswere first observed by Blackwell and Sutherland(1949). Austin and Wolfe (1956) and Wedepohl (1957)found that their intensity is related to the concentra-tion of neutral (i.e., uncompensated) boron acceptors.Smith and Taylor (1962) found that when the infraredspectrum was recorded at low temperature (−188°C),it was evident that these bands were composed ofnumerous sharp lines, the details of which are still notcompletely understood.

The basic shape of this spectrum can be explainedin terms of the energy-level diagram shown in figure A-2. The energy level of the boron acceptor is located 0.37electron volts (eV) above the valence band. The contin-uum absorption above 2985 cm−1 results from the cap-ture of electrons by boron acceptors at various depthsin the valence band; this leaves holes in the valenceband that can take part in electrical conduction, a pro-cess called photoconduction. Thermal stimulation ofelectrons from the valence band onto the acceptors alsoresults in holes in the valence band being available forelectrical conduction. The higher the temperature, thegreater the number of acceptors that are ionized, thegreater the number of holes in the valence band, and sothe higher the electrical conductivity will be.

Phosphorescence in boron-doped synthetic dia-mond has recently been studied in some detail.Whereas natural type IIb diamonds are known toexhibit both red and blue phosphorescence, synthetictype IIb diamonds always exhibit blue phosphores-cence, occasionally accompanied by orange. Both mayexhibit a greenish blue fluorescence when excited byelectrons (cathodoluminescence) or short-wave UVradiation. This luminescence has been attributed to

transitions between a donor and the boron acceptor,where the donor is believed to be nitrogen related (seeKlein et al., 1995). It has been observed that whereasthe fluorescence is also a characteristic of diamondsthat have been so heavily boron doped as to be verydark blue or black, the phosphorescence is only domi-nant and long lived in lightly boron-doped diamonds(containing less than about 10 ppm of uncompensatedboron and appearing pale blue to dark blue).

Watanabe et al. (1997) have proposed a model toexplain this phosphorescence behavior. Essentially,their recombinationmodel shows that following short-wave UV excitation and the rapid fluorescence decay,the rate of electron transition from the donor to theboron acceptor is limited by the availability of holes inthe valence band. At room temperature, only about0.2% of the boron acceptors are ionized; the lower theconcentration of these acceptors is, the lower is theprobability that the donor-to-acceptor transition canoccur. Such low-probability transitions are character-ized by long decay times, so strong, long-lived phos-phorescence is a characteristic only of lightly boron-doped material. Boron concentrations in natural typeIIb diamonds are usually a few ppm at most, and oftenconsiderably less than this, so their phosphorescencebehavior is similar to that of the lightly boron-dopedsynthetic diamonds.

Figure A-2. In this schematic energy-level diagram forthe boron acceptor in diamond, the acceptor groundstate is located 0.37 eV above the top of the valenceband. The excited-state energy levels are shown insimplified form for clarity. In fact, they are split into anumber of sublevels. Bound-hole transitions from theground state to these excited states give rise to thebands in the infrared spectrum at 2455, 2802, and2928 cm−1. If a hole is excited from the acceptorground state into the valence band, either thermallyor by photons of energy greater than 0.37 eV, itbecomes available for electrical conduction.

Boron acceptor ground-state energy level

Bound-hole transitions

Ionization

Acceptor excited-state energy levels

Hole (missing electron)

Valence bandConduction of electricity

Ene

rgy

0.37 eV


tionships of the study diamonds (see King et al.,1994). We have continued to look into instrumentalmeasurement to assist in color determinations. Todate, however, we have not identified instrumenta-tion that can adequately describe the complex face-up color appearance of a colored diamond with theperspective that an experienced observer can pro-

vide in a controlled grading environment such asthat used in our laboratory.

Standard equipment was used for gemologicaldocumentation, including a Gemolite Mark VIIbinocular gemological microscope, a GIA GEMInstruments ultraviolet unit with long-wave (365nm) and short-wave (254 nm) lamps, a desk-modelspectroscope, and a GIA GEM Instruments conduc-tometer. Electrical conductivity measurementswere made by placing the diamond on a metal baseplate and touching a probe carrying an electric cur-rent to various surfaces of the polished diamond.Because we found that in some diamonds the mea-sured conductivity values varied from one locationto the next, we made several measurements on eachstone and recorded the highest conductivity readingin our database. When documenting conductivityand reporting the results here, we used a numericalvalue that expresses the electrical current thatpassed through the diamond relative to the currentmeasured when the probe was touched to the metalbase plate (which, in this study, was always 135).This was also done to compensate for minor varia-tions in line current. Because of the difficulty ofmaking good, consistent contact between theinstrument and the diamond, these values do notrepresent a precise measurement of the electricalconductivity. At best, they provide a relative indica-tion of differences in conductivity among the bluediamonds tested.

A Hitachi U-4001 spectrophotometer was usedto collect visible absorption spectra, from 400 nm to800 nm, at low (liquid nitrogen) temperatures. To

Figure 5. Three categories of diamonds have beenassociated with a natural blue color: (1) type IIb,which are colored by boron impurities; (2) those typeIa or IIa that owe their color to radiation exposure;and (3) those type Ia in which the color is associatedwith hydrogen. Of these, only type IIb diamonds (likethat in the center) are typically described as blue(without a hue modifier) in the GIA GTL colored dia-mond color-grading system. Those naturally coloredby exposure to radiation are usually described asgreen-blue (left), whereas those colored by color cen-ters associated with hydrogen are described as gray-violet to gray-blue (right). The photo of the 1.01 ctblue marquise is by Shane F. McClure; those of the0.28 ct gray-violet heart shape and the 0.15 ct green-blue round brilliant are by Robert Weldon.

TABLE 2. Clarity, phosphorescence, and electrical conductivity of blue diamonds as they relate to GIA Gem TradeLaboratory color grades.a

GIA GTL SW UV phosphorescence SW UV phosphorescence durationcolor grade Clarity intensity (seconds)

Grade No. FL/IF VVS VS SI/I No. None Wk Med St VSt No. <5 6–15 16 –25 26–35 36–45 45+ Avg No.

Faint 9 2 3 0 4 9 0 1 1 0 0 2 — — — — — — — 0Very Light 10 2 2 2 3 9 0 2 1 0 1 4 — — — — — — — 0Light 27 5 3 6 3 17 1 7 4 0 0 12 2 0 0 1 0 0 12 3Fancy Light 44 3 6 7 5 21 2 16 0 0 0 18 4 2 1 0 0 0 6 7Fancy 226 35 28 55 18 136 5 70 16 2 1 94 9 6 2 0 0 0 8 17Fancy Intense 84 29 12 14 9 64 1 14 3 0 0 18 8 1 0 1 0 0 7 10Fancy Dark 10 1 2 0 0 3 1 3 1 0 0 5 1 2 0 0 0 0 6 3Fancy Deep 46 6 7 12 5 30 4 12 4 1 0 21 1 3 0 1 1 0 18 6Fancy Vivid 6 3 0 2 0 5 0 5 1 0 0 6 2 4 0 0 0 0 8 6

Totals 462 86 63 98 47 294 14 130 31 3 2 180 27 18 3 3 1 0 — 52

a Abbreviations: No. = number of samples tested in each subcategory, Wk = weak, Med = medium, St = strong, VSt = verystrong, Avg = average. The clarity grade ranges follow the standard GIA GTL system for clarity grading of diamonds.


investigate the relationship between the depth ofcolor and the visible absorption spectra, we selectedfour diamonds of similar size and shape but differ-ent depths of blue color (GIA GTL grades VeryLight, Fancy Light, Fancy, and Fancy Intense). Wealso tested a Fancy Light gray diamond for compari-son. We recorded the spectrum of each diamondwith the light directed into a bezel facet and emerg-ing from the pavilion facet on the opposite side. Wethen corrected the measured absorbance values forthe approximate size of the diamond. Light passingthrough a diamond does not follow a straight pathwithout any internal reflections, and a large portionof the diamond is illuminated in the instrument.Therefore, to simulate the direction and length ofthe light path through the diamond, we calculatedan approximate sample thickness as the average ofthe girdle width and the table-to-culet thickness.

For the purposes of this study, infrared absorp-tion spectra were recorded with a Nicolet Model510 FTIR spectrometer over a range of 6000 to 400wavenumbers (cm-1) on the same five diamonds forwhich visible spectra were recorded. Laser Ramanmicrospectrometry and energy-dispersive X-ray flu-orescence (EDXRF) analysis were attempted to iden-tify the inclusions in two other blue diamonds.

RESULTSColor Appearance. One of the most important partsof this study was the unique opportunity to docu-ment the range of color appearances of blue dia-monds. The study samples covered the entire rangeof GIA GTL fancy grades, as shown in figure 6.

Details of the hue (such as blue in this case), tone(the lightness or darkness of a color), and saturation(the strength of a color) of the diamonds—that is,their location in color space—are described below(again, for details on this color-grading system, seeKing et al., 1994).

Hue. The diamonds in this study typically occur ina restricted region of the hue circle (figure 7). Thissupports our past observations that the hue of typeIIb blue diamonds does not transition smoothlyinto the neighboring color hues (i.e., their hue doesnot extend into violetish blue in one directionaround the hue circle, or into greenish blue in theother direction). Within this region of the hue circle,there are two narrow populations. The fact thattype IIb blue diamonds occur within such narrowranges is very different from the situation with yel-low diamonds, in which subtle hue shifts are seenthroughout its hue range.

Tone and Saturation. Figure 8 shows the generallocation of the blue diamonds in our study on atone and saturation grid. Of the three colorattributes, blue diamonds showed the greatest varia-tion in tone: The samples covered a broad light-to-dark range.

Compared to other colors in diamond, however,a relatively narrow range of appearance distinctionswas seen for the saturation of blue diamonds. Forexample, at its widest region—i.e., corresponding tosuch GIA GTL fancy grades as Fancy, Fancy Intense

Figure 6. This pie chart illustrates the percentagesof the 462 blue diamonds studied that appearedin each GIA GTL fancy grade category.

Electrical conductivity GIA GTLvaluesb color grade

10–30 31–50 51–70 71–90 90+ Avg No. Grade

— — — — — — 0 Faint— — — — — — 0 Very Light3 4 2 0 0 41 9 Light4 7 11 3 1 56 26 Fancy Light12 31 35 17 8 60 103 Fancy3 7 7 8 3 64 28 Fancy Intense0 0 5 2 1 76 8 Fancy Dark1 3 6 6 6 77 22 Fancy Deep2 1 1 1 1 62 6 Fancy Vivid

25 53 67 37 20 — 202 Totals

b All 462 samples were electrically conductive.

Faint 2%

Very Light 2%

Light 6% Fancy Light

10%

Fancy Dark 2%

Fancy Intense 18%

Fancy Deep 10%

Fancy Vivid 1%

Fancy 49%


or Fancy Deep, and Fancy Vivid—the saturationrange for blue diamonds is less than one third thatin which yellow diamonds occur. This compressedsaturation range means that the degree of differ-ence in color appearance within each GIA GTLfancy grade is much narrower for blue diamondsthan for yellow diamonds. For example, the rangeof appearances between Fancy Deep yellow andFancy Vivid yellow is broader than the rangebetween Fancy Deep blue and Fancy Vivid blue.

For the diamonds in our study, and in our gener-al experience, we found that there are four smallerclusters in color space where blue diamonds mostcommonly occur. These are indicated on the grid in

figure 8 by the circles.GIA GTL fancy grades represent a combined

effect of tone and saturation (King et al., 1994).Figure 9 shows the general relationship of the

YELLOW

GREENISH YELLOW

GREEN YELLOW

YELLOW GREEN

YELLOWISH GREEN

GREEN

BLUISH GREEN

BLUE GREEN

GREEN BLUE

GREENISH BLUEBLUE

VIOLETISH BLUE

BLUISH VIOLET

VIOLET

PURPLE

REDDISH PURPLE

RED PURPLE

PURPLE RED

PURPLISH RED

ORANGY RED

REDDISH ORANGE

ORANGEYELLOWISH

ORANGEYELLOW ORANGE

ORANGE YELLOW ORANGY

YELLOW

RED

Figure 7. The blue dia-monds studied appear togroup into two narrow,restricted populations(indicated by the arrows)within the range of colorGIA GTL associates withthe term blue. This isunlike the broader occur-rence within the hueranges of other coloreddiamonds, such as yel-low, that we haveencountered.

SATURATION

TONE

Lighter

Darker

Lower Higher

BLA

CK

NE

UT

RA

LG

RA

YW

HIT

E

Figure 8. The beige area on this grid illustrates thetone and saturation range observed for the blue dia-monds in this study. Note that the tone values occur

over a broader range than the saturation values.Within this area are four smaller clusters (here, shown

as circles) in which the colors of blue diamonds aretypically observed.

FA

INT

VE

RY

LIG

HT

LIGHT

FANCY LIGHT

FANCY

FANCY INTENSE

FANCY DEEPFANCY DARK

FANCY VIVID

Figure 9. The images of bluediamonds superimposed onthis chart of GIA GTL fancygrades illustrate the range ofcolors seen to date in bluediamonds. Note that thefancy-grade terms have ageneral relationship to thetone/saturation grid shownin figure 8. For example, thelighter, least saturated bluediamonds are in the upperleft (Faint or Very Light),whereas the darker, mostsaturated blue diamondsfall toward the lower right(Fancy Deep to FancyVivid). For the purposes ofthis illustration, the sizes ofsome of the diamonds werealtered relative to oneanother. It also should benoted that these imageswere compiled over severalmonths. It may not be pos-sible to find such a com-plete range of fancy gradesin the market at a giventime. Photos by Harold &Erica Van Pelt, RobertWeldon, Shane F. McClure,and Maha DeMaggio.


images of several blue diamonds superimposed on achart of the GIA GTL fancy-grade categories. Such achart illustrates the subtle distinctions in colorappearance between the various “fancy” terms.

Microscopic Examination. Clarity. As shown in fig-ure 10, 29% of the 294 diamonds analyzed for clari-ty were Flawless or Internally Flawless; 84% wereVS or higher (these data include diamonds in whichclarity could potentially be improved even furtherby the removal of shallow imperfections). Thesepercentages are much higher than we have observedin other diamonds. The high clarity grades of thesepolished blue diamonds are consistent with thehigh “purity” (i.e., clarity) of the rough as comparedto most other diamonds (D. E. Bush, pers. comm.,1998).

Inclusions. In the subset of 62 diamonds that weexamined specifically for inclusions, we found thatapproximately 35% (22) had no inclusions. Of theremaining stones, 78% had fractures or cleavagesand only 25% had solid inclusions (and, in somecases, fractures or cleavages as well). In the smallpercentage of blue diamonds that contained solidinclusions, the tendency was for the inclusions tohave a consistent shape and appearance. The inclu-sions in figure 11 are typical of those observed.

They tend to be opaque, dark, platy in habit, andwould best be described as “flakes” with a slightlyrough surface. They have an almost hexagonal,somewhat geometric outline. At magnificationhigher than 10×, the outlines are jagged and appearto be composed of interconnected and overlappingplates. When examined with reflected fiber-opticillumination, the inclusions appear gray and theroughness of the surface becomes most apparent.

With magnification and polarized light, theopaque inclusions are surrounded by visible strainhalos composed of low-order interference colors.The inclusions do not align with any linear strainpattern of the host diamond. Instead, they seem tointerfere with the otherwise orderly arrangement ofthe crystal structure, causing additional strain tothe host crystal.

Since GIA acquired its Raman spectroscopy sys-tem in the fall of 1997, there has been limitedopportunity to analyze the solid inclusions in bluediamonds. Raman analysis of solid inclusions intwo diamonds proved inconclusive because of thesmall size of the inclusions and the fact that theirrough surfaces caused the laser beam to scatterrather than return to the detector. The resultingRaman spectra were of poor quality and such weakintensity that they could not be matched with thespectral features of likely inclusion materials (suchas graphite or a sulfide mineral inclusion; see fol-lowing paragraph). EDXRF chemical analysis of theinclusions also was not diagnostic. For both tech-niques, the composition and size of the inclusion,its depth below the surface of the diamond, and itslocation within the diamond were all factors thatprevented successful analysis.

From our visual observations of these inclusionswith respect to their luster, dark color, morphology,and lack of transparency, we believe that the inclu-sions are either a sulfide or graphite (see, e.g., Harris,1972; Meyer and Tsai, 1976). The fact that theinclusions are positioned in seemingly randomdirections, and they cut across distinct linear strainplanes in the diamond, suggests that they are sul-fides, because graphite forms most commonly alongcleavage planes as a result of diamond alteration(see Harris, 1972; Harris and Vance, 1972; andMeyer and Tsai, 1976). Graphite inclusions wouldbe expected to follow the planar structures in a dia-mond, rather than cutting across those layers. Theexcessive strain surrounding each of these inclu-sions also supports their identification as sulfides.Graphite forming as an alteration product along

Flawless or Internally Flawless

29%

VVS 21%

VS 34%

SI/I 16%

Figure 10. This pie chart illustrates how the 294 bluediamonds in this study that were clarity graded fitinto the various GIA GTL clarity grade ranges.Although marketing factors may influence theseresults, the most surprising feature of this diagram isthe very high percentage of diamonds in theFlawless/Internally Flawless category (much greaterthan for other diamonds).


planes in the diamond would not be expected toproduce detectable strain in the host, whereas visi-ble strain halos around sulfide inclusions are typical(J. I. Koivula, pers. comm., 1998).

Graining. Internal graining is more common in bluediamonds than in near-colorless type Ia diamonds.Readily noticeable graining—which would carry acomment of “internal graining is present” on thereport—was seen in approximately one-fourth ofthe 40 sample diamonds that had internal features.Graining is commonly believed to result from irreg-

ularities in the crystal structure that form during orafter crystallization. In our samples, the grainingmost often appeared as whitish bands (figure 12) orreflective internal planes.

Color Zoning.We saw color zoning, often very sub-tle, in more than 30 of the 62 diamonds in theinclusion subset. This zoning was most easily seenwith diffused lighting and darkfield illumination. Ittypically appeared as discrete blue and colorlessareas or parallel bands (figure 13). When cuttingsuch a diamond, manufacturers try to locate the

Figure 11. In 10 of the blue diamonds examined for inclusions in this study, we observed dark solid inclu-sions. On the left are several such inclusions in a 1.22 ct Fancy blue diamond. On the right is an isolatedexample of a flattened inclusion in a 4.57 ct Fancy Intense blue emerald cut. Visual examination suggeststhat these are probably sulfide mineral inclusions. Photomicrograph on the left is by Nick DelRe, magni-fied 30×; right, by Vincent Cracco, magnified 63×.

Figure 12. This Fancy Deep blue diamond, whichweighs more than 10 ct, exhibits parallel bandsnear the culet. Such graining is not uncommon inblue diamonds. When graining is this extensive, itaffects the clarity grade. Photo by Vincent Cracco;magnified 10×.

Figure 13. Color zoning is often observed in blue dia-monds. This photograph, taken at 10×magnification,shows parallel banding of colorless and blue areas.The position of the zones can have a significantimpact on the face-up color (but typically not the clar-ity) of the diamond. Photo by Stephen Hofer, © GIA.


Like many other aspects of blue diamonds, the manu-facturing processes (planning, cutting, and polishing)often follow a path different from those used for near-colorless diamonds and even other fancy colors. Severalfactors must be considered. First, the rough usuallylacks a symmetrical form (figure B-1), unlike type Ia dia-monds which often occur in common habits such asoctahedra or dodecahedra. Thus, it may be more diffi-cult than normal to determine appropriate cleaving andpolishing directions. Second, the blue color may beunevenly distributed: Color zoning frequently occursalong growth directions or in isolated regions, often asalternating blue and near-colorless bands. Orientingthese color zones to obtain the best face-up color appear-ance is a challenge similar to the cutting and polishingof blue sapphire, but the much higher value of blue dia-monds (in which every point removed could mean aloss of thousands of dollars) means that the conse-quences are far more serious. Third, the surfaces ofstrongly asymmetric diamonds are commonly sculptedand translucent (Orlov, 1977). Thus, the cutter mustpolish several “windows” on the crystal to see any colorzoning and inclusions before planning the cut.

These manufacturing challenges make moderncomputer-assisted cutting programs such as the SarinDia-Expert (Caspi, 1997) less useful in planning cuts forblue rough. Larger blue rough sometimes is shaped firstin a rudimentarymanner, maintaining flexibility regard-ing the final shape until the cutter can see the internalfeatures more clearly. One may start out with plans foran oval or perhaps a pear shape, but make the final deci-sion late in the faceting process. Weight recovery isoften less than that typically obtained with colorless tonear-colorless octahedral diamond rough.

The final face-up color of a blue diamond is much

less predictable than most diamonds in the D-to-Zrange or even than other fancy colors because of suchfeatures as color zoning. However, modern cutting andpolishing techniques used to retain, improve, and spreadcolor in all fancy-color diamonds also apply to blue dia-monds. These techniques include the adaptation of“half-moon” facets and French culets to nearly allknown brilliant-cut designs and shapes (figure B-2). Half-moon-shaped facets are cut along the girdle on the pavil-ion (on straight or curved sides), usually at high anglesrelative to the girdle plane. These half-moon facets cre-ate more internal reflection, which produces a moreintense face-up color appearance. A French culet dis-tributes the color more evenly throughout.Conventional pavilion faceting typically concentratesthe color in the points, corners, or heads of longershapes such as ovals and pears. The color in the center(under the table) is weaker, creating an uneven two-toneeffect. The French culet reduces this collection of colorat the point and, with the half-moon facets, can preventloss of color in the center of the faceted diamond.

Because of the irregular shape of the rough, the pol-ishing directions are often difficult to orient. A cuttermust be conscious of heat build-up and surface burningfrom misorientation on the polishing wheel, especiallywhenworking on large facets such as the table.

The fact that blue diamonds occupy a small regionof color space means that subtle changes in appearancecan influence the color description or grade. After decid-ing on a final shape, the cutter methodically adjusts thepavilion and crown angles, factoring in any previousexperience with those angles in similarly colored rough.Often each side is cut to different angles, and the result-ing effects on color appearance are compared. In fact, insome cases this asymmetrical faceting is left on the fin-ished stone. Manufacturing blue diamonds is often aslow, arduous process that requires careful inspection ofthe face-up color appearance at each stage.

BOX B: MANUFACTURING BLUE DIAMONDS

Figure B-1. These rough blue diamonds (approxi-mately 0.75 to 2.00 ct) are typical of the irregularshapes, color zoning, and sculpted, translucent sur-faces associated with this material.

A

B

Figure B-2. Theuse of a Frenchculet (A) andhalf-moonfacets (B) onthe pavilionoften creates ablue diamondwith a stronger,more evenlycolored face-upappearance.


color zoning strategically to give the stone a uni-form, more saturated blue appearance when it isviewed face-up (see Box B).

Fluorescence/Phosphorescence. Ninety-eight per-cent of the diamonds in this study showed noobservable fluorescence to long-wave UV, and 91%showed no observable fluorescence to short-waveUV. However, subtle fluorescence was difficult toobserve because of the blue bodycolor combinedwith the purple surface reflections from the UVlamps. Of the small number of diamonds that didshow a readily observable fluorescence to long- orshort-wave UV radiation, the reaction was chalkyblue to green or, rarely, red; the intensity was weak.It should be mentioned that extremely weak fluo-rescence in a diamond could be recorded as “none”on a GIA GTL report. Thus, the actual percentagesof diamonds that fluoresce is likely to be higherthan the values given above.

As is typical of type IIb blue diamonds, there wasalmost never a phosphorescence to long-wave UV,but a reaction to short-wave UV was common(again, see table 2). In fact, it was usually much easi-er to see phosphorescence from our samples than tosee fluorescence. Of the blue diamonds that phos-phoresced (92%), the reaction varied from veryweak to very strong, with almost three-quartersshowing a very weak or weak reaction. The mostcommon color was the same as the fluorescencecolor, chalky blue to green; rarely, it was red ororangy red. Because the important criterion in ourtypical gemological examinations of blue diamonds

is whether or not a phosphorescent reaction isnoted, for this study we recorded the duration of thephosphorescence in a random subset of 52 bluediamonds. The duration varied from a few seconds toas long as 45 seconds. Within the subset, we alsonoted that the Fancy Deep diamonds had the mostpersistent phosphorescence, at an average of 18 sec-onds. During our most recent examination of the(Fancy Deep) Hope diamond, we checked this featureclosely and noted that the total phosphorescence,whichwas red, actually lasted almost 45 seconds.

Electrical Conductivity. All the diamonds in ourstudy were electrically conductive. The samplesshowed a wide range of measured values, both ingeneral and within each fancy-grade category (seetable 2). The lowest value measured among oursamples was 10:135, and the highest was 120:135(again, reading on the diamond and reading on themetal plate).

As mentioned above, we sometimes noted avariation in conductivity within individual stonesby touching the probe to different areas. A goodexample is the data we recorded for the Hope dia-mond in 1996, as shown in figure 14.

Visible Absorption Spectrum. Type IIb blue dia-monds lack sharp absorption bands in their visiblespectra. Rather, they exhibit a gradually increas-ing absorption toward the red end of the spec-trum. Figure 15 shows the absorption spectra offour blue diamonds of differing intensities and agray diamond.

40:135

30:135

Metal Base Plate

DIAMOND POSITION 1

45:135

65:135

70:135

DIAMOND POSITION 2

Figure 14. Type IIb bluediamonds are electricallyconductive. In some cases,different locations on thesurface of the diamonddiffer in conductivity.

Shown here are the resultsof conductivity measure-ments recorded for vari-

ous locations on thefamous Hope diamond.On the basis of our con-

vention to record the high-est number obtained

through repeated mea-surements, the number

recorded for the Hope was70:135.


Infrared Absorption Spectrum. Figure 16 showsthe mid-infrared spectra of the same five diamondsfor which the visible spectra were illustrated in fig-ure 15. The features that are characteristic of atype IIb diamond were more intense in the twodiamonds with a stronger blue color relative to theother diamonds.

DISCUSSIONType IIb blue diamonds are unique in a number oftheir gemological properties, such as their electricalconductivity together with their phosphorescenceto short-wave UV. This allows for their separationfrom other materials more readily than is the casefor many gems. In addition, diamonds of other typesthat are described as blue typically are not of thesame hue, nor do they have similar reactions toother gemological tests. Therefore, this studyfocused less on the identification of natural fromtreated or synthetic blue diamonds and more onunderstanding their distinctive color appearance.Because of the critical role that color plays in theevaluation of type IIb blue diamonds, the followingdiscussion will examine the relationship of the vari-ous color appearances to the characteristics docu-mented in natural type IIb blue diamonds.

Color Relationships Among Blue Diamonds. Animportant goal of this study was to better under-stand how blue diamonds relate to one another in

color space—that is, hue, tone, and saturation—especially as these relationships are articulated inthe GIA GTL color grading system for colored dia-monds.

Hue. From the tight hue clustering found in the typeIIb blue diamonds studied, it appears that boron, theelement that causes the color (again, see Box A), cre-ates a very limited range of color appearance.

Tone and Saturation. For many people, tone andsaturation are the most difficult aspects to discrimi-nate in the face-up color appearance of a facetedgemstone. Because the hue range is limited, thevariation in color appearance among blue diamondsis mainly determined by the tone and saturation oftheir colors. In the GIA GTL grading system, a vari-ety of color appearances can be included within thesame fancy grade. The system uses the same set offancy grades for describing all colored diamonds, butfor blue diamonds, these grades are compressed intoa smaller region of color space.

As the results of this study indicate, the colors oftype IIb blue diamonds occur in a relatively widetone range (i.e., light to dark) but a narrower satura-tion range (i.e., weak to strong intensity) in colorspace (see again figure 8). Because of this distribu-tion, the color appearances that one usually sees inblue diamonds are more likely to result from differ-ences in tone (see figure 17). For an unfamiliar

400 450 500 550 600 650 700 750 8000

0.2

0.1 ADCBE

Wavelength (nm)

Ab

sorb

ance

Figure 15. The visible spectra of blue diamonds lack sharp absorption bands; rather, they have graduallyincreasing absorption toward the red end of the spectrum. Spectra A to D are for blue diamonds of differingcolor intensity (A=Fancy Intense, B =Fancy, C =Fancy Light, and D =Very Light); spectrum E is for a FancyLight gray diamond. These spectra were recorded at low (liquid nitrogen) temperature. The diamonds, all ovalor marquise shapes of similar weights and proportions, were positioned so that light entered a bezel facet andexited an opposite pavilion facet. Each of these spectra was normalized to the approximate sample pathlength, so the spectra could be compared. Because of the similarity of the spectra from one sample to the next,we could not correlate them with the depth of color in the five diamonds. However, this similarity in spectrais consistent with the narrow range of color appearances in which blue diamonds occur.


observer of blue diamonds, differences in tone canbe misinterpreted as saturation differences.

As mentioned earlier, the colors of most bluediamonds tend to be concentrated around four clus-ters on the tone/saturation grid (see again figure 8).This clustering can cause misconceptions about thecolor grades of blue diamonds. For example:

1. Some of these clusters fall across grade bound-aries. In this situation, subtle differences in colorappearance between two blue diamonds canresult in their being described with differentfancy grades (figure 18). Judging from the morecommon situation involving yellow diamonds,some people may expect the differences in colorappearance for some blue diamonds with differ-ent grades to be more pronounced than is actual-ly the case.

2. When one looks at two blue diamonds that fallwithin the same cluster on the tone/saturationgrid, at first these two colors may look sufficient-ly different that the observer feels that twogrades are warranted. However, when the colorsof these two blue diamonds are compared to thatof a third diamond that is noticeably different inappearance, the close correspondence in color ofthe first two becomes apparent (figure 19). In thissituation, use of two grades to describe the colorsof blue diamonds that occur within the samecluster is not warranted.

3. In contrast to the colors of blue diamonds thatfall within a cluster, a situation can occur wherethe color of a less-commonly seen blue diamondfalls outside one of the four clusters. Despite thedifferences in appearance, these blue diamondscould still be assigned the same grade.

It is also important to recognize that the narrowsaturation range in which blue diamonds occur isrelatively close to the neutral gray region of colorspace. In general, the eye can discern fewer colordistinctions in this region. Again, though, the tradeexpects—and an orderly description systemimplies—an equal number of grades for blue dia-monds as for other colors despite the inequalitybetween respective areas of color space. For a bluediamond and a yellow diamond in the same grade,the color of the yellow diamond is relativelystronger so the color differences between grades aremore readily perceived.

Consequently, our experience with blue dia-monds suggests the following:

Wavenumbers (cm-1)

Ab

sorb

ance

A

D

C

B

E

6000 5000 4000 3000 2000 1000

Figure 16. The mid-infrared spectra of the five dia-monds for which visible spectra are presented in fig-ure 15 reveal the pattern of absorption features that ischaracteristic of type IIb diamonds. These featuresare most intense for the two stronger-blue diamonds(spectra A and B).


1. Color grading of blue diamonds requires use of acontrolled methodology and grading environ-ment to ensure the maximum consistency andrepeatability.

2. To evaluate the significance of a differencebetween two colors, it is important to have refer-ences of known color location in color space forbracketing (see figure 20).

Clarity. The fact that blue diamonds are generallyof high clarity is related to their type, not theircolor. Other type II diamonds, such as colorless typeIIa diamonds, as well as some pink diamonds fromIndia (Scarratt, 1987), show the same high clarity.

Marketing decisions made by the manufacturer alsoprobably influence this high clarity. That is, insome sizes, it may be that some markets prefer bluediamonds that are smaller but flawless to those thatare larger and of lower (SI and below) clarity (M.Kirschenbaum, pers. comm., 1998). Ultimately, aswith other colored diamonds, color is by far themost important factor.

Correlations of Depth of Blue Color and OtherGemological Properties. With the large number ofblue diamonds available for study, we were able toestablish some general correlations between depthof color and other properties (again, see table 2).

Figure 17. These fourFancy blue diamonds(from left to right, 2.03,0.48, 2.01, and 1.15 ct)are similar in saturation,but they differ in tone;that is, they become pro-gressively darker fromleft to right. These differ-ences might be misinter-preted as increasing satu-ration by an inexperi-enced observer. Photo ©Harold & Erica Van Pelt.

Figure 18. Colored diamonds located near fancy-grade terminology boundaries may appear similaryet still be described differently in the GIA GTLgrading system. Because of the narrow saturationrange in which blue diamonds occur, this effect isheightened, as the fancy-grade saturation bound-aries are closer together than for other colored dia-monds. The two diamonds shown here are of simi-lar tone and differ slightly in saturation. Becausethey are near a fancy-grade boundary, the 1 ctmarquise shape diamond on the left is describedas Fancy blue and the (more saturated) 0.78 ctpear shape on the right is Fancy Intense blue.Photo © Harold & Erica Van Pelt.

Figure 19. Because of the clustering in tone and satu-ration encountered with blue diamonds, those in sim-

ilar clusters (such as the two diamonds on the left,1.19 and 2.03 ct) may initially appear to differ in

depth of color more than they actually do, since theobserver has a natural tendency to make distinctions.When a diamond of different tone and saturation (farright, 1.82 ct) is placed next to them, the similarities

between the first two become clearer. Unlike the situ-ation in figure 18, these first two diamonds were notnear a grade boundary, so both were graded Fancy

blue. Photo © Harold & Erica Van Pelt.

Phosphorescence. In general, the Fancy Deep bluediamonds had the longest lasting phosphorescence.There was no clear correlation between intensity ofphosphorescence and strength of color (more than50% across all grades showed weak phosphores-cence).

Electrical Conductivity. While it is difficult toestablish a direct relationship (partly due to theproblems encountered in obtaining consistent mea-surements, as mentioned above), the general trendamong our samples was for the blue color to bedarker and/or stronger as the electrical conductivityincreased. There are exceptions to this behavior, ascan be seen by the measurements recorded for indi-vidual diamonds within a grade range (see table 2).Also, we have noted several highly conductive darkgray (i.e., unsaturated) diamonds, and we recently

encountered a Fancy Light blue diamond with aconductivity value that was similar to those ofmany of the blue diamonds graded as Fancy Deep orFancy Dark.

Although electrical conductivity is not a com-pletely accurate indicator, diamond manufacturersoccasionally use strength of conductivity to identifypotentially stronger and weaker areas of color in therough diamond (K. Ayvazian, pers. comm., 1998).They believe that in combination with visual obser-vations of color zoning, this can be helpful in pro-ducing the most saturated face-up color appearancepossible in the finished diamond (again, see Box B).

Visible and Infrared Spectra. Comparison of thefive spectra in figure 15 shows very little differencein absorption. We could not completely correlatethe intensity of the face-up color of these five dia-


Figure 20. For centuries,people have devised ways

to understand colorappearance relationships

through various ordersystems such as those

shown in the backgroundof this photograph.

Understanding the colorordering of gems is partic-ularly important for grad-ing blue diamonds. The

bracelet contains a 3.56 ctFancy Dark gray-blue ovalbrilliant with 30.87 caratsof D-color, internally flaw-less pear brilliants. In thethree rings are a 2.87 ct

Fancy Deep blue emeraldcut, a 1.64 ct Fancy gray-

blue marquise, and a12.38 ct Fancy blue rect-

angular modified brilliant.The three unmounted pear

brilliants are a 1.02 ctFancy blue, a 4.02 ct

Fancy Intense blue, and a15.29 ct Fancy blue.

Courtesy American SibaCorp. and Rima Investors

Corp. Photo byRobert Weldon.


monds (as expressed by the fancy grade description)and their spectra. This lack of correlation can beattributed to several factors. First, these spectrawere recorded for a light path through the bezel and

pavilion facets of the stone in an attempt to mea-sure the bodycolor. The color grade, however, wasestablished by visual observation of the face-upcolor. Second, the face-up color appearance of a col-

TABLE 3. Blue diamond identification.

Property Natural diamonda Natural diamonda Treated diamondb Synthetic diamondc

Type IIb IIa or Ia IIa or Ia IIbColor Pale to deeply Pale to deeply colored Pale to deeply colored Pale to deeply

colored blue green-blue and, rarely, green-blue and, rarely, colored blueblue to violet blue

Cause of color Trace amounts of boron Radiation exposure Radiation exposure Trace amounts of boronSize of cut stones To more than 50 ct Up to 20 ct Depends on sample Less than 1 ct

selected for treatmentFeatures seenwith magnification

Color Often even, sometimes Even, sometimes uneven Even, sometimes uneven Usually uneven, withdistribution uneven with blue/ with blue and near- with blue and near-color- blue and near-colorless

colorless zoning colorless zones; color less zones; color zoning may zones related to internalzoning may be located follow faceted shape— growth sectors; may formnear surface radiation often concentrated at cross-shaped patternstains the culet

Graining Sometimes whitish Occasional planar Not diagnostic Planar graining markingreflective or transparent graining, sometimes boundaries of color zoning,graining colored or, rarely, may form cross-- or hourglass-

whitish shaped patternsInclusions Usually free of mineral Sometimes mineral Sometimes mineral Elongated or rounded

inclusions; sometimes inclusions inclusions opaque metal inclusions, opaque black isolated or in small inclusions groups; occasional

pinpointsOther internal Occasional fractures Occasional fractures, Occasional fractures, Generally free of fractures features or cleavages cleavages, pinpoints, cleavages, pinpoints, and cleavages

clouds cloudsStrain Weak to strong Weak to strong Weak to strong Weak anomalous

anomalous double anomalous double anomalous double double refraction,refraction, sometimes refraction, sometimes refraction, sometimes sometimes in a crossin parallel or crossin parallel or crossin parallel or cross- patternhatched patterns hatched patterns hatched patterns

Visible No sharp bands, Sometimes weak to Sometimes weak to No sharp bands, absorption increasing absorption strong bands (415, strong bands (415, increasing absorptionspectra toward the red end 478, 496, 504, 478, 496, 504, toward the red end of

of the spectrum 595 nm) 595 nm) the spectrumUltraviolet Usually none, rarely Sometimes weak to Sometimes weak to Weak to moderate blue toluminescence weak red to orange-red, strong blue, greenish strong blue, greenish greenish blue to SWUV;

occasionally blue to blue, green, yellow, blue, or green uneven distribution relatedgreenish blue to SWUV or orange to internal growth sectors

Phosphor- Blue to green, rarely None None Moderate to strong blue,escence red to orangy red sometimes with orange;

persistent durationCathodo- Usually greenish blue, Not examined Not examined Weak to strong greenishluminescence sometimes shows blue; sometimes with un-

cross-hatched pattern even distribution related to internal growth sectors; some sectors show no reaction

Other features Electrically conductive Green or brown radiation May exhibit residual Electrically conductive,stains on surface or radioactivity may be attracted by aalong open fractures strong magnet

a Adapted from Shigley et al. (1995) and (for natural type IIb blue diamonds) based on data gathered for this study.b Based on data accumulated at the GIA Gem Trade Laboratory and GIA Research.c Based on observations by GIA Research and the DTC Research Centre.


ored diamond is determined not just by the bodycol-or but also by effects of the faceting style and thelighting and observation conditions. Nonetheless,the overall similarity of these five spectra lends sup-port to the results of the visual observation portionof this study, that the range of color appearancesfrom gray to gray-blue to blue is limited.

Although the infrared spectra of all 5 stoneswere similar, we did note that the type IIb featureswere most prominent in the two diamonds with thestrongest blue color.

Identification and Separation. The properties andappearance of type IIb blue diamonds do not typical-ly overlap with those of treated blues, and synthetictype IIb blue diamonds are not available on the com-mercial market. Still, it is valuable to understand theseparation of these diamonds. Table 3 presents abrief comparison of the gemological properties ofnatural, treated, and synthetic blue diamonds.

SUMMARY AND CONCLUSIONThe special qualities of blue diamonds, and the richhistory associated with many of them, has madesuch diamonds highly valued and desirable in thegem and jewelry industry today. The earliest refer-ences to blue diamonds came centuries ago, whenthe Tavernier Blue was brought from India.Although blue diamonds have occasionally beenreported from sources other than the Premier minein South Africa, this historic mine has producedmost of the blue diamonds seen in the marketplace.Currently an underground operation, the Premiermine is viable primarily because of the handful ofblue or large colorless “specials” that are recoveredeach year.

Because virtually all the diamonds described asblue by the GIA Gem Trade Laboratory are type IIb,we chose to focus on this type for our study. In addi-tion to their unique color attributes, type IIb dia-monds have distinctive traits such as electrical con-ductivity, boron as the coloring agent, and a charac-teristic phosphorescent reaction to short-wave UV.Fancy Deep blue diamonds had the longest phos-phorescence, but there was no correlation to inten-sity of the phosphorescence. Also, there was a trend

among the samples for diamonds that were astronger and/or darker blue to have higher electricalconductivity. We have found that blue diamondstypically are of higher clarity than other diamonds.However, the fact that the rough may be colorzoned and is typically irregular in shape makes themanufacturing of these diamonds challenging.

A key goal of this study was to provide a betterunderstanding of the narrow color range in whichtype IIb blue diamonds occur and the color appear-ances associated with their various GIA GTL fancygrades. Blue diamonds are unique among coloreddiamonds in that they occupy isolated regions intheir hue range and primarily occur in four smalltone/saturation clusters. If we understand this, wecan understand how these diamonds relate to oneanother and to diamonds of other colors.

Acknowledgments: At the GIA Gem TradeLaboratory (GIA GTL), Thomas Gelb, Scott Guhin,and Joshua Cohn assisted with visual color observa-tions and analysis. Mark Van Daele and Kim Cinoperformed database analyses, and Elizabeth Doyle,Giulia Goracci, Sam Muhlmeister, and Shane Elenassisted in the data collection. John Koivula per-formed inclusion analysis and commentary. Dr.Emmanuel Fritsch, of the University of Nantes,France, offered comments on the text. BasilWatermeyer, of Steinmetz-Ascot, Johannesburg,South Africa, provided information on manufactur-ing blue diamonds. Dr. Jeffrey E. Post, curator ofgems and minerals at the Smithsonian Institution,Washington, DC, supplied information on the Hopediamond. Sam Abram of American Siba Corp., AraArslanian of Cora Diamond Corp., MartinKirschenbaum of M. Kirschenbaum Trading, AliKhazaneh of Rima Investors Corp., and Isaac Wolfloaned diamonds for this study and offered valuablecomments. Special thanks for helpful discussions toGareth Penny, diamond consultant, and David E.Bush, senior divisional diamond revenue manager,De Beers Corporate Headquarters, Johannesburg; andAngus Galloway, general manager, and MikeSemple, market controller, Harry OppenheimerHouse, Kimberley, South Africa. Hans Gastrow, gen-eral manager of the Premier mine, South Africa, pro-vided a tour of the mine and production information.

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270 Fingerprinting of Two Diamonds GEMS & GEMOLOGY Winter 1998

ypically, two faceted stones are cut from one well-formed diamond crystal. Yet each takes a differentroute in the market, with little chance of both dia-

monds being set together in a single piece or related pieces ofjewelry. However, if two such diamonds were set in twopieces of jewelry worn, for example, by a mother and adaughter, this might provide additional sentimental value tothe stones. Keeping two such diamonds together is possibleonly when the piece of rough is cut under the dealer’s con-trol. Even so, scientific documentation is necessary to provethis shared origin. Plotting a diamond’s internal features (asin a diamond grading report) may help identify a single stone,but it cannot prove that two diamonds came from the samerough. More advanced techniques are needed for this task.

Natural crystals do not grow at a constant rate or underconstant conditions. Rather, crystals may experiencegrowth-rate fluctuations, gentle or abrupt changes in growthparameters, or partial dissolution and regrowth during theirformation. As a result, physical imperfections and chemicalinhomogeneities—such as inclusions, lattice defects (pointdefects, dislocations, and planar defects), and chemicalimpurities—are induced in crystals during their growth andpostgrowth histories. These characteristics are uniquely dis-tributed within each crystal as growth sectors (zonal struc-tures), intrasectorial zoning, growth banding, and nonuni-form distributions of elements, color, or luminescence;these features are not modified during later cutting and pol-ishing processes (Sunagawa, 1984a, 1988; Scandale, 1996;and the references therein). Consequently, they are the mostreliable diagnostic features for fingerprinting stones (and fordistinguishing natural from synthetic gem minerals; see,e.g., Sunagawa, 1995), provided they can be determined non-destructively.

We report in this article how we verified that two dia-monds—a round brilliant and a pear-shaped brilliant—camefrom the same piece of rough, by revealing the spatial distri-

If it can be determined that two faceted dia-monds came from the same piece of rough,romantic value is added to the stones. X-raytopography and cathodoluminescence (CL)tomography were used to prove that a roundbrilliant and a pear-shaped brilliant were cutfrom the same piece of rough. With these tech-niques, the internal imperfections and inho-mogeneities that reflect the distinctive growthhistory of the original diamond crystal can beseen. X-ray topography is a powerful tool forimaging the distribution of lattice defects; CLtomography is more sensitive for detectingfaint chemical inhomogeneities. By combin-ing the two methods, the sophisticated gemol-ogist can view both physical and chemicalcharacteristics of a crystal, and thus its growthhistory, and use this information to fingerprinta given stone.

T

FINGERPRINTINGOF TWO DIAMONDS

CUT FROM THE SAME ROUGHBy Ichiro Sunagawa, Toshikazu Yasuda, and Hideaki Fukushima

ABOUT THE AUTHORS

Dr. Sunagawa is principal of the YamanashiInstitute of Gemmology and Jewellery Arts inKofu, Japan, and professor emeritus of mineral-ogy at Tohoku University, Sendai, Japan. Mr.Yasuda recently retired from the GeologicalSurvey of Japan in Tsukuba, Ibaraki Prefecture,where he was a specialist in the X-ray topogra-phy of crystals. Mr. Fukushima is a member ofthe Education Department at the GemmologicalAssociation of All Japan in Tokyo, where he hastaken thousands of cathodoluminescencetomographs of faceted diamonds.

The authors express their thanks to Mr. M.Ishida of ExRoyal Inc., New York, for providingthe samples.

Gems & Gemology, Vol. 34, No. 4, pp. 270–280© 1998 Gemological Institute of America

Fingerprinting of Two Diamonds GEMS & GEMOLOGY Winter 1998 271

bution of lattice defects (using X-ray topography)and those of cathodoluminescence-emitting centers(using CL tomography). Both methods were appliedwithout any damage to the stones.

The study was initiated when a dealer claimedthat two brilliant-cut diamonds he was offeringwere from the same rough. After X-ray topographyproved otherwise, the dealer traced the route thetwo stones had taken from the cutter, and eventual-ly he found another brilliant that produced an X-raytopograph that matched one of the previous bril-liants. After establishing the characteristics of thesethree diamonds by X-ray topography, the authorsapplied CL tomography to provide supporting evi-dence for the initial conclusions. The characteris-tics observed with these two techniques vividlydemonstrate the different growth histories of differ-ent diamond crystals. This example also demon-strates the usefulness and applicability of X-raytopography and CL tomography in gemology.

MATERIALS AND METHODSSamples. The first pair of diamonds offered by thedealer, samples A and B, had the following charac-teristics recorded on their GIA Gem TradeLaboratory (GIA GTL) grading reports:

Sample A: Round brilliant; 1.08 ct; 6.59–6.62 ¥4.10 mm; E color; VSl clarity; 62.1% depth, 56%table, thin-to-medium faceted girdle, no culet;excellent polish; very good symmetry; no fluo-rescence (report dated February 9, 1993).

Sample B: Pear-shaped brilliant; 0.81 ct; 8.03 ¥5.54 ¥ 2.93 mm; E color; VSl clarity; 52.9%

depth, 55% table, thin-to-thick faceted girdle,very small culet; good polish; good symmetry;no fluorescence (report dated January 4, 1993).

As described below, it was proved that these twodiamonds were not cut from the same piece ofrough. Subsequently, the dealer traced the stonesback to the manufacturer and submitted the follow-ing diamond, sample C:

Sample C: Round brilliant; 1.05 ct; 6.43–6.67 ¥4.01 mm; E color; VSl clarity; 60.3% depth, 59%table, very thin-to-thin faceted girdle, smallculet; excellent polish; very good symmetry; nofluorescence (report dated January 25, 1993).

Samples A, B, and C are shown in figure 1. They arevery clean to the naked eye and, as evident from theGIA GTL grading reports, no internal flaws are dis-cernible with the microscope, other than pinpointinclusions. Nevertheless, X-ray topography and CLtomography (as described below) revealed distinc-tive internal heterogeneities and imperfections.

Experimental Procedures. X-Ray Topography. Byidentifying contrasts in X-ray reflection, X-raytopography can detect and record the spatial distri-bution of strain fields associated with various lineardefects (e.g., dislocations) and planar defects (e.g.,stacking faults and twin planes) in single crystals. Inother words, X-ray topography reveals the distribu-tion of deviations from the ideal lattice plane. Theterm topography is used to describe the three-dimensional nature of these data.

Since X-ray topography is a well-established

Figure 1. These three dia-monds, all from the same

manufacturer, were studiedto determine which two, if

any, were cut from the samepiece of rough. All of the

diamonds were graded as Ecolor and VS1 clarity.

Sample A (left) weighs 1.08ct, sample B (center) is 0.81

ct, and sample C (right)weighs 1.05 ct. Samples B

and C were proved to origi-nate from the same rough

diamond.

Figure 2. This schematic diagram illus-trates the geometry generally adoptedto obtain X-ray topographs (after Lang,1978). In the present study, a faceteddiamond was used in place of the crys-tal plate, with the table facet parallelor perpendicular to the plate (see figure3). X-rays are passed through a narrowslit and reflected through the sample,off one selected lattice reflectionplane, to produce a three-dimensionalimage of the crystallographic imperfec-tions and inhomogeneities on the X-ray film. The three-dimensional imageis obtained by scanning the entiresample, through synchronous move-ment of both sample and film.

Figure 3. For this study, {110} and{111} crystallographic planes

(dashed lines) were selected as thelattice reflection planes (left). The

orientation of two of the a-axesare shown. Two directions of the

incident X-ray beams were used inthis study—parallel and perpen-

dicular to the table facet (horizon-tal and vertical, respectively). The

schematic diagram on the rightshows the viewing geometry for

the samples. The round brilliantindicates the positions of samples

A and C, and the pear-shaped bril-liant indicates sample B. The two

directions of view in the corre-sponding X-ray topographs are

indicated by the eyes. Note thatthe reflection plane {220} is

expressed as {110} for simplicity inthis article; {110} does not reflect

X-ray beams, but {220} does.

method, this article will not give a detailed descrip-tion of its principles and methods. Interested readersmay refer to review papers by Frank and Lang (1965)or Lang (1978, 1979).

In the present study, the Lang method (1978)was used to record the X-ray topographs (see figure2). The sample is typically cut into a plate for analy-sis, but complete crystals or faceted stones can beused if the sample is small; good topographs can beobtained for diamonds up to about 2 ct. A narrow,ribbon-like beam of X-rays with a fixed wavelength

is passed through a narrow slit and scanned over thesample at a fixed incident angle (i.e., in a reflectionorientation). Only those X-ray beams that matchthe ideal reflection of the lattice plane are reflectedoff this plane and recorded on the X-ray film.Distorted lattice portions (i.e., those that deviatefrom the ideal reflection plane) appear as contrast-ing images on the film (white on the negative, orblack on the print), thus revealing the spatial distri-bution of lattice defects in the sample. The X-raysused in this study were produced with an accelerat-



ing voltage of 50 kV and a current of 1 mA.For X-ray topography, the system operator must

select appropriate lattice reflection planes, takinginto consideration the angles and intensities ofreflecting beams and the distortion of imagescaused by the oblique scanning angle. Assumingthat the table facet in each stone was approximatelyparallel to a (100) plane, we selected {110} and {111}directions as reflection planes. (Note that the reflec-tion plane {220} is expressed as {110} for simplicityin this article; according to the extinction rule, {110}does not reflect X-ray beams, but {220} does.) This isshown schematically in figure 3. As figure 4 illus-trates, the images are distorted depending on thedirection of the reflection. This distortion must betaken into consideration when the X-ray topographsfor two different stones are compared. To obtainimages with good contrast, the researcher usuallyprepares a plate from the sample that is of appropri-ate thickness (depending on the material, e.g., 1 mmfor quartz). This, of course, is not possible with pol-ished gemstones. However, because goodtopographs can be achieved with relatively thicksamples of diamond, we were able to obtain usefulimages from the faceted stones examined for thisstudy.

Cathodoluminescence Tomography. After we hadanalyzed all three samples by X-ray topography, weused CL tomography as a supporting method. Withthis technique, one can see the heterogeneous dis-tribution of CL-emitting centers in a solid material,up to a few micrometers below the surface. Becauseof the limited depth of penetration, this techniqueis referred to as tomography, since it reveals onlythe two-dimensional distribution of the CL-emit-ting centers in a plane near the surface. CL tomogra-phy has been used widely in solid-state physics andthe earth sciences (see, e.g., Davies, 1979; Lang,1979), and Ponahlo (1992) has also applied it togemology.

A scanning electron microscope (SEM) or opticalmicroscope is used to observe the images generatedby CL tomography. The present study used the lat-ter, a Premier American Technologies Co.Luminoscope. Because of its lower vacuum, theLuminoscope is not as sensitive as an SEM system,but it is adequate for this type of problem. Also, thesamples do not need to be carbon-coated (as theywould for SEM analysis). CL tomography does notautomatically identify the elements responsible forthe CL emission; nor does it give quantitative data

for their concentrations. The CL intensities may cor-respond semi-quantitatively to the concentrations ofthe CL-emitting centers, but other methods, such asspectroscopy, are required to identify the chemicalelements or obtain quantitative data. However, forthe purpose of this study—that is, visualizing thedistribution of CL-emitting centers in different dia-monds—quantitative analyses were not needed.

RESULTSX-Ray Topography. Samples A and B. X-raytopographs of sample A, taken with {110} and {111}

Figure 4. X-ray topographic images are distortedbecause of the oblique reflection of the vertical X-ray beam. Here, three schematic diagrams—eachlabeled with the corresponding reflection plane—{110} or {111}—illustrate the positions of the tablefacet (small circles) and the girdle outline; the pro-file of each stone is also shown. All three imagesare produced using the same (vertical) incident X-ray direction; the particular image obtaineddepends on the reflection plane selected. Note thatthe image in 2 is inverted relative to 1. Actual X-ray topographs corresponding to these threeimages are shown in figure 5.


lattice reflections, show a few dislocations that arenearly parallel to {110}, and straight growth bandsparallel to {111}, planes (figure 5). The dislocationsradiate from a point slightly above the table facet;this point marks the center of an octahedral crystal,from which the dislocations progressed nearly per-pendicular to the growing octahedral {111} faces.

X-ray topographs of sample B (figure 6) aremarkedly different from those of sample A. The

sample B topographs reveal dislocation bundles thatare much greater in number and density than thosein sample A. Moreover, the dislocations in sample Bare parallel to <100>, not to {110} as in sample A.The dislocation bundles originate not from a pointcenter, but from the boundary of a square-shapedcore. Faint growth banding is discernible in areasbetween the dislocation bundles, but these are moreevident on CL tomographs (see below). The growth

Figure 5. These three X-ray topographs of sample A were taken with different reflection planes, as shown in fig-ure 4 (images 1, 2, and 3). The green arrows indicate dislocations, and the white arrows indicate growth banding.An idealized illustration of the dislocations is shown for topograph 3, in plan view and in profile. The two dislo-cation bundles are inferred to meet at a position slightly above the table facet.

Figure 6. These two X-ray topographs of sample Bwere taken with two (110) reflection planes. Alarge number of dislocations (dark heavy lines)originate from the boundaries of a square-shapedcore, and form bundles nearly parallel to the a-axes. Faint zigzag patterns are also visible betweenthe dislocations. Note the marked difference ofthese topographs from those of sample A shown infigure 5, with respect to the presence of a core por-tion, the number and orientation of dislocations,and the modes of growth banding.

Figure 7. These X-ray topographs of sample C cor-respond to the same orientation and reflectionplanes as those shown in figure 6 for sample B.Note the close similarity to sample B in the pres-ence of a square-shaped core portion, the densityand orientation of dislocation bundles, and thefaint zigzag patterns between the dislocations. Theclose resemblance shown by these topographs(considering that both diamonds had some materi-al polished away) indicates that samples B and Ccame from the same rough.


banding is not straight, but rather shows a zigzagpattern. The differences in the X-ray topographs ofsamples A and B suggest that they could not haveoriginated from the same piece of rough.

Sample C. X-ray topographs of sample C (figure 7)show dislocation bundles originating from theboundary of a square-shaped core and running paral-lel to <100>, as well as faint zigzag patterns in theareas between the dislocation bundles. By compar-ing the topographs of samples B and C, one can seethat the presence of the square-shaped core, the ori-entation and spatial distribution of the dislocations,and the faint zigzag growth banding seen in thesediamonds, are essentially the same. This impliesthat these two diamonds were cut from the samepiece of rough.

Closer observation of the core portions of sam-ples B and C confirms their similarity (figure 8). Inboth samples, the dislocation densities are muchhigher in the surrounding portion than in the core.Although most of the dislocations in the core con-tinue into the surrounding portion of the diamond,it is clear that most of the dislocations outside thecore are generated along the boundary between thecore and the surrounding diamond. It is also evidentthat the core portion was bounded by somewhatrugged cuboid faces. The characteristics and sizes ofthe core portions of samples B and C match perfect-ly, if the volume of the portion that was polishedaway from both samples is taken into consideration.

In profile view, X-ray topographs of samples Band C at the same orientation also show good corre-lation in the morphology and position of the coreand the spatial distribution of dislocation bundles(figure 9). In addition, one notices that the tablefacets of the two stones are inclined slightly (about6°–7°) from the (100) face. This inclination may bedue to the cutter’s desire to avoid inclusions thatwere originally present in the rough, or simply toobtain a higher yield from odd-shaped rough.

The results of our X-ray topographic investiga-tions are summarized in figure 10. The images con-clusively indicate that samples B and C came fromthe same diamond rough, whereas sample A camefrom a different piece of rough.

CL Tomographs. By comparing CL tomographs ofsamples A, B, and C (figure 11) with their X-raytopographs, one immediately notices the following:1. Only blue cathodoluminescence of varying inten-

sities was observed; no yellow, green, or red.

2. Straight (sample A) or zigzag (samples B and C)growth banding, which was faintly visible onthe X-ray topographs, was more readily seen onthe CL tomographs (as alternating bright anddark bands).

3. The square-shaped core present on the CLtomographs of samples B (at the center of thetable facet) and C (at the upper left of the tablefacet) is not visible in sample A, on either the X-ray topographs or the CL tomographs.

4. Although growth banding typically is easier tosee on CL tomographs than on X-ray topographs,

Figure 8. These X-ray topographs have beenenlarged to show the core portions of samples Band C. Sample B is shown in plan view (X-raybeam perpendicular to the table facet), and sam-ple C is shown in profile view (X-ray beam parallelto the table facet), as in figure 9. The truncation ofsample C near the top of the topograph corre-sponds to the surface of the table facet, whichshows a slight inclination relative to the (100)face. The white lines indicate the corners of theboundary of the square-shaped core, and the whitearrows indicate dislocations that begin in the coreand continue into the surrounding diamond.Enlarged approximately 30¥.


the radiating dislocations that are clearly visibleon the X-ray topographs of samples A, B, and Ccould not be resolved on their CL tomographs.

5. In sample A, alternating bright and dark CLzones are straight and parallel to {111}. In bothsamples B and C, two different types of growthzoning can be distinguished on the CL tomo-graphs. One type is visible between neighboringareas of the second set as short, fairly straight,bright and dark CL zones parallel to <110>. Inthe second set, bright and dark zones with a

zigzag pattern are present within the <100>zones, which correspond to the location of dislo-cation bundles seen on the X-ray topographs.(Note: Since {100} faces are never present assmooth, flat faces on natural diamond crystals[Sunagawa, 1984b], they are customarily called“cuboid” faces. For simplicity, we refer to themhere as <100> zones instead.)At higher magnification, CL images of the core

portions of samples B and C revealed these addition-al features (figure 12):

Figure 9. These X-ray topographs show twoprofile views of sample B (top) and sampleC (bottom). The topographs are oriented toshow the faceted diamonds as they werepositioned in the original crystal, with thea3 axis indicated by the arrow in the cen-ter. The topographs on the right show thesamples rotated 90° from those on the left;the crystallographic orientation betweenthe upper and lower views is identical.There is a high degree of correlationbetween the two diamonds in the charac-ter and orientation of the dislocations. Thecore portion is difficult to see in sample B,because most of it has been polishedaway. Note also that the table facet isinclined about 6°–7° from the crystallo-graphic (100) plane.

Figure 10. These diagramsschematically illustrate

the three-dimensionalnature of the dislocations

revealed by X-ray topogra-phy in the three samples.

On the left, the appear-ance and orientation of

the dislocations in sampleA (bottom) are much dif-ferent from those in sam-

ple B (top). On the right, aperfect match is evident

for samples B and C in thepresence of a cuboid-

shaped core and the anal-ogous dislocation bundles.


6. The distribution of bright and dark areas is lessheterogeneous in the core portion than in thesurrounding areas.

7. Around the perimeter of the core is a brightcathodoluminescence zone, which indicates ahigh concentration of CL-emitting centers atthis boundary.

8. In the <100> growth sectors, where bundles ofdislocations are visible on the X-ray topograph,bright and dark zones in the shape of a zigzag—or short right angles—appear alternately orintermittently. The segments are parallel to<110> (i.e., they consist of segmental {111}planes).

9. In the <110> growth sectors (i.e., in the areasbetween the neighboring <100> growth sectors),short or long bright CL bands appear parallel to<110>. These bands do not show a zigzag pat-tern, but rather they have a tabular form. Thesefeatures correlate to a high concentration of CL-emitting species. The intervening dark bandscorrelate to zones that lack CL-emitting centers.

10. Both the straight bands and the zigzag segmentsare parallel to <110> (i.e., to {111} planes). Eachstraight band or segment corresponds to a smallinternal {111} face. Since they appear as brightCL bands, the {111} faces are apparently associ-ated with incorporation of CL-emitting species.

Figure 12. At greater magnification (approximately 25¥), the CL tomographs of samples B and C show thedark, roughly square-shaped core and surrounding brighter CL-emitting areas. Crystallographic directions<100> and <110> are indicated. Note the bright and dark zigzag patterns in the <100> sectors and the tabularpatterns in the <110> sectors.

Figure 11. The distribu-tion of CL-emitting cen-

ters is visible on these CLtomographs. Note the

marked differencebetween sample A (e.g.,

straight growth zones,absence of a square-

shaped core) and samplesB and C (e.g., zigzag

growth zones and thepresence of a square-

shaped core—in the cen-ter of the table of sampleB and in the upper left of

the table in sample C).A B C

B C

<100>

<110><100>

<110>


DISCUSSIONFingerprinting Faceted Diamonds. Several featuresobserved with X-ray topography and CL tomogra-phy prove that samples B and C were cut from thesame piece of diamond rough, whereas sample Acame from a different crystal. In general, the spatialdistribution and orientation of dislocations, thepresence or absence of a square-shaped core, and thecharacteristics of growth banding were distinctivefor these samples.

Although the present case is unambiguous, itmight be asked whether such fingerprinting is uni-versally applicable. The answer is “yes,” since eachnatural single crystal experienced its own uniquegrowth or post-growth history, which is recorded inits internal imperfections and inhomogeneities.With careful investigation, one can conclusively fin-gerprint a stone or a set of stones, even if two stonesshow quite similar internal features.

Applying X-Ray Topography and CL Tomographyin Gemology. Crystallographic imperfections andinhomogeneities are distinctive features that can bevisualized using instruments available in manystandard gemological laboratories (such as the hori-zontal microscope with immersion; see, e.g.,Schmetzer 1996; Smith, 1996). However, X-raytopography allows the visualization of three-dimen-sional lattice imperfections—such as dislocations—that are not easy to visualize by other methods. CLtomography shows near-surface chemical inhomo-geneities two-dimensionally. Both methods can beused to distinguish natural from synthetic dia-monds (as well as any other gemstone), since ineach case the crystals grow from different mediaand under different conditions (Lang et al., 1992;Sunagawa, 1995, 1998).

In general, X-ray topography is more informativethan CL tomography. Although most major gemo-logical laboratories have the capitalization to installa Lang configuration for X-ray topography (whichcan cost from $50,000 to about $100,000), the tech-nique requires a thorough knowledge of crystallog-raphy and diffraction, and it is somewhat time con-suming to adjust the crystallographic orientation ofa sample to obtain good topographs.

CL tomography, in combination with opticalmicroscopy, is also affordable (about $25,000) formost major gemological laboratories, and it doesnot require much background knowledge.Although it cannot reveal the spatial distribution of

dislocations as effectively as X-ray topography, it isuseful in fingerprinting a stone or a set of stones.Furthermore, CL data can, independent of X-raytopography, conclusively separate natural fromsynthetic diamonds (Ponahlo, 1992; Sunagawa,1995).

Growth History. These techniques also provide use-ful information about the formation of natural dia-mond crystals. Arguments over the origin of naturaldiamonds began long ago (e.g., Fersman andGoldschmidt, 1911), and still continue (Frank andLang, 1965; Lang, 1978, 1979; Lang et al., 1992;Sunagawa, 1984b, 1988, 1995; Sunagawa et al., 1984).

Although we did not identify the CL-emittingspecies in this study, or determine their concentra-tions, it is commonly known that blue cathodolu-minescence is principally due to nitrogen (probablya combination of band-A and N3 centers) and thatCL intensities correspond semi-quantitatively tonitrogen contents (Clark et al., 1992). Higher con-centrations of nitrogen are assumed for the zonesshowing brighter CL images than for the darkerzones. The CL observations in the present studyindicate that nitrogen incorporation into the grow-ing diamond crystal fluctuated intermittently, withthe boundaries between the CL zones representingthe positions of growing surfaces at various stages.Such fluctuations are universally observed in natu-ral crystals.

Two distinctly different growth histories wereidentified for the diamonds in the present study (fig-ure 13). In sample A, alternating bright and dark CLzones form a straight pattern parallel to {111}throughout the stone, which indicates that a sim-ple, unmodified octahedral crystal habit was main-tained throughout its entire growth history.Dislocations originate from a central point and areoriented perpendicular to {111}. These indicate thatthe crystal did not experience an abrupt change ingrowth parameters to modify the habit. Such a situ-ation corresponds to the growth of crystals under anear-equilibrium condition at a small driving force(low supersaturation or low degrees of supercool-ing). Dislocation patterns of this type are commonlyencountered in octahedral crystals of natural dia-mond (see, e.g., Frank and Lang, 1965; Lang, 1978).They have been identified as screw-type disloca-tions in single-crystal octahedral diamonds fromSiberia (Sunagawa et al., 1984), which proves thatthe natural diamond crystals investigated grew by


the spiral growth mechanism. The straight growthbands parallel to {111} are commonly encounteredin single-crystal natural diamond, and they indicatea layer-by-layer (including spiral) growth mecha-nism on {111}, such that the octahedral habit wasnot modified throughout the growth history(Sunagawa, 1984b). It should be noted that evenunder such a steady growth condition, the nitrogenpartitioning fluctuated, as shown by the alternatingbright and dark CL zones. Such a zonation isattributed to local fluctuations in the growth rate.

Samples B and C showed a square-shaped coreportion and much denser dislocation bundles in the<100> directions. Since most dislocations originateat the core boundary, there must have been aninterruption of growth between the core and thesurrounding material. A possible explanation is thatthe core formed under one set of growth conditions,

and then was transported to a new growth environ-ment where it acted as a seed for further diamondgrowth. This is the first observation of the presenceof a seed crystal in natural diamond crystal growth.

The core took a cuboid form, bounded by roughcuboid surfaces (Sunagawa, 1984a), rather than anoctahedral form. Further diamond growth on thisseed transformed the morphology from cuboid tooctahedral, or dodecahedral truncated by cuboidfaces (i.e., that of a mixed habit). At the onset ofgrowth over the cuboid seed, nitrogen was incorpo-rated isotropically (i.e., equally over the seed surface,independent of crystallographic direction) into thecrystal, giving rise to a bright CL band surroundingthe seed surface. This also implies an abrupt changeof growth parameters, which was followed by theappearance and development of {111} faces. In <110>growth sectors, {111} faces are flat; whereas in <100>

Figure 13. Samples B and C were cut from a crystal with a different morphology—and a more complicatedgrowth history—than sample A. As shown on the left, sample A had a simple octahedral habit, bounded by{111} faces that grew by the spiral growth mechanism from the outcrop of dislocations. Several outcroppingdislocations (the straight lines with triangular terminations) are shown, along with only one triangulargrowth spiral; each dislocation would be expected to produce a similar growth spiral during crystal growth.Samples B and C are assumed to have been cut from a dodecahedroid crystal with a rounded morphologythat was due to post-growth dissolution of a crystal that originally consisted of stepped octahedral faces(equivalent to {110} faces) that were truncated by rough cuboid faces (right). The cuboid-shaped core acted asa seed for further growth of the surrounding portion. The straight lines that extend from the core to the cuboidface are dislocation bundles. Only part of the complicated growth history for this crystal is shown.


growth sectors, {111} faces are segmental. Also in the<100> growth sectors, the cuboid surface transformedinto segmental {111} subfaces, while maintaining thegeneral cuboid surface. It is likely that the growth of{100} cuboid sectors was not governed by the spiralgrowth mechanism. Although a large number of dis-locations outcropped on the growing surface, they didnot act as sources of spiral growth steps. The differ-ence observed in interface roughness and growth pro-cess between {111} and {100} in sample A and sam-ples B and C is in agreement with results reportedpreviously by Sunagawa (1984b, 1995).

CONCLUSIONSThe spatial distribution of dislocations and the het-erogeneous distribution of CL-emitting centerswere determined for three diamonds by means of X-ray topography and CL tomography. On the basis ofthese results, and information given by the dealer,

we concluded that two of these diamonds were cutfrom the same piece of rough, whereas the third wascut from a different crystal. Two distinctly differentgrowth histories were revealed for the original crys-tals. One grew by the spiral growth mechanism onoctahedral faces under near-equilibrium conditions,and the other showed growth of octahedral ordodecahedral forms on a cuboid seed. The advancedtechniques employed require that the user have atechnical background, but the equipment is afford-able for most major gemological laboratories

Although the demand for fingerprinting faceteddiamonds will depend on market preference, thewriters believe that the techniques used in thisstudy are important for the future development ofgemology. Ongoing research (e.g., Sunagawa, 1998)is investigating the use of X-ray topography and CLtomography for distinguishing natural from syn-thetic gem materials.

REFERENCES

Clark C.D., Collins A.T., Woods G.S. (1992) Absorption andluminescence spectroscopy. In J.E. Field, Ed., The Propertiesof Natural and Synthetic Diamond, Academic Press, London,pp. 35–80.

Davies G. (1979) Cathodoluminescence. In J.E. Field, Ed., TheProperties of Diamond, Academic Press, London, pp.165–184.

Fersman A., Goldschmidt V. (1911) Der Diamant. Carl Winter’sUniversitätbuchhandlung, Heidelberg.

Frank F.C., Lang A.R. (1965) X-ray topography of diamond. In R.Berman, Ed., Physical Properties of Diamond, ClarendonPress, Oxford, pp. 69–115.

Lang A.R. (1978) Techniques and interpretation in X-ray topogra-phy. In S. Amelinckx, R. Gevers, and J. van Landuyt, Eds.,Diffraction and Imaging Techniques in Material Science, Vol.II, North-Holland, Amsterdam, pp. 623–714.

Lang A.R. (1979) Internal structure. In J.E. Field, Ed., TheProperties of Diamond, Academic Press, London, pp.425–469.

Lang A.R., Moore M., Walmsley J.C. (1992) Diffraction and imag-ing studies of diamond. In J.E. Field, Ed., The Properties ofNatural and Synthetic Diamond, Academic Press, London,pp. 215–258.

Ponahlo J. (1992) Cathodoluminescence (CL) and CL spectra ofDeBeers experimental synthetic diamonds. Journal ofGemmology, Vol. 23, No. 1, pp. 3–18.

Scandale E. (1996) X-ray Topographic Method for Minerals.

Lecture notes of Short Course on Crystal Growth in EarthSciences, Santa Vittoria d’Alba, Italy, 14–19 April, pp.361–374.

Schmetzer K. (1996) Growth method and growth-related proper-ties of a new type of Russian hydrothermal synthetic emerald.Gems & Gemology, Vol. 32, No. 1, pp. 40–43.

Smith C.P. (1996) Introduction to analyzing internal growthstructures: Identification of the negative d plane in naturalruby. Gems & Gemology, Vol. 32, No. 3, pp. 170–184.

Sunagawa I. (1984a) Growth of crystals in nature. In I. Sunagawa,Ed., Materials Science of the Earth’s Interior, Terra, Tokyoand D. Reidel, Dordrecht, pp. 63–105.

Sunagawa I. (1984b) Morphology of natural and synthetic dia-mond crystals. In I. Sunagawa, Ed., Materials Science of theEarth’s Interior, Terra, Tokyo and D. Reidel, Dordrecht, pp.303–330.

Sunagawa I. (1988) Morphology of minerals. In I. Sunagawa, Ed.,Morphology of Crystals, Part B, Terra, Tokyo and D. Reidel,Dordrecht, pp. 509–587.

Sunagawa I. (1995) The distinction of natural from synthetic dia-monds. Journal of Gemmology, Vol. 24, No. 7, pp. 485–499.

Sunagawa I. (1998) Imperfections and inhomogeneities in singlecrystals as a basis to distinguish natural from synthetic gem-stones. Zeitschrift der Deutschen GemmologischenGesellschaft, Vol. 47, No. 1, pp. 45–52.

Sunagawa I., Tsukamoto K., Yasuda T. (1984) Surface microtopo-graphic and X-ray topographic study of octahedral crystals ofnatural diamonds from Siberia. In I. Sunagawa, Ed., MaterialsScience of the Earth’s Interior, Terra, Tokyo and D. Reidel,Dordrecht, pp. 331–349.

Notes and New Techniques GEMS & GEMOLOGY Winter 1998 281

ABOUT THE AUTHORS

Mr. Koivula ([email protected]) is chief research gemologistat the GIA Gem Trade Laboratory in Carlsbad, California.Mr. Elen is research gemologist at GIA Research, Carlsbad.

Please see acknowledgments at the end of the article.

Gems & Gemology, Vol. 34, No. 4, pp. 281–283.© 1998 Gemological Institute of America

have required that the host be damaged by cleavingor grinding to expose the inclusions for X-ray pow-der diffraction and/or chemical analysis. Given theapparent rarity of the specimen, we decided to keepthe sample intact until a nondestructive means ofanalysis became available at GIA.

NOTES AND NEW TECHNIQUES

BARITE INCLUSIONS IN FLUORITEBy John I. Koivula and Shane Elen

During the 1984 Tucson Gem and Mineral Show,one of the authors (JIK) discovered an interestingspecimen while examining a large selection ofIllinois fluorites for mineral and fluid inclusions.This 247.02 ct partial crystal, which measured 36mm on its largest dimension, was transparent andhad a rich, slightly brownish yellow color. Whatmade it interesting, however, was the presenceunder a cube face of two prominent white, hemi-spherical aggregates of an unknown mineral (figure1). Because no similar inclusions were seen in anyof the other fluorite crystals, the unusual specimenwas acquired for further investigation.

These inclusions resembled the fibrous whitebarite aggregates that had been previously observedon fluorite specimens from Illinois (Goldstein, 1997;Ross Lillie, pers. comm., 1998). Because neitherinclusion reached the surface of the fluorite, howev-er, conclusive identification at that time would

Hemispherical aggregates of the mineral barite were identified as inclu-sions in fluorite from Illinois. One of these inclusions showed a dramaticpseudo-color change because of its position in the host. The identificationof these inclusions was made nondestructively using laser Ramanmicrospectrometry.

Figure 1. Two large inclusions, which Ramananalysis proved to be barite, are easily seen in this247.02 ct specimen of Illinois fluorite. Photo byMaha DeMaggio.

282 Notes and New Techniques GEMS & GEMOLOGY Winter 1998

More than a decade later, in 1995, gem cutterMichael Gray showed one of the authors (JIK) anunusual 99.49 ct faceted fluorite from Illinois (figure2) with a white 7.5 mm inclusion that was visuallyidentical to the two inclusions described above.This sample was even more unusual, however,because the inclusion appeared to show a colorchange from purple in incandescent light to blue influorescent illumination (figure 3).

In April of 1996, R. C. Feather described somevoids in fluorite from Illinois that had the sameshape as the mineral inclusions described here. In

that article (p. 12), Mr. Feather speculated that thevoids might once have been occupied by the miner-al barite because of “the form and the fact thatbarite is known to occur in the area.”

MATERIALS AND METHODSThe large “white” inclusions in both the original247.02 ct partial crystal and the 99.49 ct faceted flu-orite were examined with a standard gemologicalmicroscope and analyzed by laser Raman micro-spectrometry. In preparation for Raman analysis,both samples were first cleaned in acetone and thencarefully examined with magnification to positionthe inclusions as close to the surface as possible andto determine the best angle from which to analyzethem. This is necessary to minimize matrix effectsfrom the fluorite host. We used a mounting clay toplace the fluorite samples on glass microscopeslides during analysis. Because the inclusions wereso large, we were able to study them using the 20¥objective lens of the Leica targeting microscope,which allowed a greater depth of focus and laserpenetration into the fluorite host than the 50¥ lenswe typically use. Further details on the Ramantechnique as applied to gemology can be found inSchubnel et al. (1992) and Hänni et al. (1997).

Using the continuous scan feature and the 514nm argon laser of the Renishaw Raman system, weperformed 10 complete scans of the inclusions ineach of the two samples. The peak-search programemployed used the Raman system’s software inconjunction with the Renishaw digital spectrallibrary. As a control, we also analyzed a crystal ofbarite from Colorado under the same conditions.

Figure 3. The 7.5-mm-long barite inclusion shown in figure 2 appears purple in incandescent light (left) andblue in fluorescent light (right). This pseudo-color change is imparted to the white inclusion by reflectionfrom the fluorite host, which shows the actual color change. Photomicrographs by John I. Koivula.

Figure 2. This 99.49 ct fluorite contains a white7.5 mm inclusion, also identified as barite, thatreflects the color of the surrounding fluorite.Photo by Maha DeMaggio.

Notes and New Techniques GEMS & GEMOLOGY Winter 1998 283

RESULTS AND DISCUSSIONStandard examination with magnification revealedthat the color change in the inclusion in the facetedfluorite was not a phenomenon of the inclusionitself; rather, it was caused by the position of theinclusion with respect to the color zoning of the flu-orite host. The base of the inclusion rested in a zoneof brownish yellow fluorite that comprised theentire pavilion of the stone, giving the fluorite abrownish yellow color face up (again, see figure 2).The upper portion of the inclusion was enclosed ina fluorite color layer that showed a strong purple-to-blue color change. The white inclusion served as anexcellent background on which to display this dra-matic change of color.

The Raman analysis revealed a spectral matchfor barite in each of the three inclusions (figure 4).All of the major peaks for barite were present in allof the analyses. Slight differences were notedbetween the spectra obtained for the barite inclu-sions and the barite control sample, but these aredue to the fluorite matrix and to differences in opti-cal and crystallographic orientation (i.e., anisotropyof Raman spectra).

As noted earlier, voids shaped like barite aggre-gates have been described and illustrated in fluorite(Feather, 1996). A search of the literature, however,failed to turn up any photographic documentationof actual barite inclusions in fluorite, althoughGoldstein (1997) briefly mentions them. No descrip-tion of any association between change-of-color flu-orite (Gübelin and Schmetzer, 1982) and barite as aninclusion was found. Therefore, the 99.49 ct facetedgem, which dramatically displays its color changeby reflection from a white barite inclusion, may beunique.

Acknowledgments: The authors thank Michael Grayof Graystone Enterprises, Missoula, Montana, forcalling attention to the unusual faceted fluorite.Russell Feather, gemologist at the Smithsonian

Institution (Washington, DC) and Dr. Carl Francis,curator of the Harvard Mineralogical Museum(Cambridge, Massachusetts), provided backgroundinformation on the rarity of large barite inclusions influorite. Ross Lillie, a geologist in West Bloomfield,Michigan, supplied information about the occurrenceof barite with fluorite. This study would not havebeen possible without the generous support ofMichael M. Scott of Los Altos, California, for hisdonation of the Renishaw Raman ImagingMicroscope System to GIA Research.

Figure 4. This representative Raman spectrumof the white inclusions in the two fluorite sam-ples (top) is nearly identical to the spectrum forbarite that was used as a reference sample (bot-tom). The additional peaks (e.g., at 320, 912,and 947 cm-1) in the Raman spectrum of thebarite inclusions are due to anisotropy ofRaman spectra and matrix effects from the sur-rounding fluorite.

REFERENCES

Feather R.C. II (1996) Inclusion of the month: Phases in fluorite.Lapidary Journal, Vol. 50, No. 1, p. 12.

Goldstein A. (1997) The Illinois-Kentucky fluorite district.Mineralogical Record, Vol. 28, No. 1, pp. 3–49.

Gübelin E.J., Schmetzer K. (1982) Gemstones with alexandrite

effect. Gems & Gemology, Vol. 18, No. 4, pp. 197–203.Hänni H.A., Kiefert L., Chalain J.P. (1997) A Raman microscope

in the gemmological laboratory: First experiences of applica-tion. Journal of Gemmology, Vol. 25, No. 6, pp. 394–406.

Schubnel H.J., Pinet M., Smith D.C., Lasnier B. (1992) Lamicrosonde Raman en gemmologie. Revue de Gemmologie,special issue.

284 Lab Notes GEMS & GEMOLOGY Winter 1998

Maxixe BERYL, Faded and Fading

Recently, the West Coast laboratorywas asked to identify the 8.10 ct lightgreenish blue gemstone shown infigure 1. The refractive indices of1.580–1.590 and uniaxial optic char-acter suggested beryl, an identifica-tion confirmed by a specific gravityvalue (measured hydrostatically) of2.80. Magnification revealed needles,growth tubes, angular growth planes,and pinpoints, thus proving that thiswas a natural gemstone. The color fellin the typical range for aquamarine,although the refractive indices, bire-fringence, and specific gravity wereslightly higher than expected for thatvariety of beryl.

The spectrum visible through adesk-model spectroscope did notshow the line at 427 nm, which is

related to the iron that causes blue inaquamarine. Instead, we saw fourdistinct bands between 550 and 700nm that are characteristic of bothnatural-color dark blue beryl from theMaxixe mine in Brazil and beryl treat-ed to this color (see K. Nassau et al.,“Deep-blue Maxixe-type color centerin beryl,” American Mineralogist,Vol. 61, 1976, pp. 100–107). A visiblespectrum obtained with a Hitachi U-4001 spectrophotometer showedbands at 581, 617, 655, and 696 nm,with additional (weaker) peaks at553, 592.5, 605, and 630 nm. Thistype of beryl typically showspleochroism with a stronger colorseen along the optic axis direction(the opposite of aquamarine, inwhich the stronger pleochroic coloris seen looking perpendicular to theoptic axis). However, the color of thisstone was so pale that no pleochroismwas observed.

Except in rare cases, dark blue isan unstable color in beryl; it fades inbright light or on exposure to heat,whether it is produced by treatmentor by natural irradiation (K. Nassau,“On the identification and fade test-ing of Maxixe beryl, golden beryl andgreen aquamarine,” Journal ofGemmology, 1996, Vol. 25, No. 2, pp.108–115). It is likely that the lightgreenish blue color of this 8.10 ctberyl is what remained after such fad-ing. The greenish component in par-ticular can arise when previously irra-diated beryl is heated to temperaturesunder 300°C (G. Mathew et al.,“Maxixe-type colour centre in natural

colourless beryl from Orissa, India:An ESR and OA investigation,”Journal of Gemmology, Vol. 26, No.4, 1998, pp. 238–251). However, wecould not prove this nor ascertainwhether any additional fading mightoccur, so we included a comment onthe report about possible color insta-bility.

Shortly thereafter, a client submit-ted three blue beryls, reportedly fromBrazil, to the West Coast lab forexamination, with permission tocarry out fade testing on one of them,a 3.34 ct oval. The gemological prop-erties were within the usual range forberyl, and the spectra were similar tothat described above. We compared thesamples to Munsell color chips andrecorded their hue, tone, and satura-tion; then we photographed them. Theinitial appearance of the 3.34 ct oval isshown in figure 2 (left). We placed it ina solar simulator, exposing it to brightlight (approximately D65, i.e., day-light-equivalent). After four hours, thecolor was substantially less saturatedand lighter in tone, so the gemappeared paler and grayer. An addi-tional four hours of exposure causedfurther fading (figure 2, right).

CYW and IR

Editor’s note: The initials at the end of each itemidentify the editor(s) or contributing editor(s) whoprovided that item.Gems & Gemology, Vol. 34, No. 4, pp. 284–289©1998 Gemological Institute of America

Figure 1. This 8.10 ct light green-ish blue free-form mixed-cutberyl was of the Maxixe-type,rather than an aquamarine. Thiscolor probably represents theresult of fading.

Lab Notes GEMS & GEMOLOGY Winter 1998 285

DIAMONDBrown with Green-to-Blue Color ZonesFrom time to time, both laboratoriesexamine diamonds with a concentra-tion of green to blue at the culet oralong the keel that suggests laborato-ry irradiation (see, e.g., E. Fritsch andJ. E. Shigley, “Contribution to theidentification of treated colored dia-monds: Diamonds with peculiarcolor-zoned pavilions,” Gems &Gemology, Vol. 25, No. 2, 1989, pp.95–101). The East Coast laboratoryrecently received two diamonds fromthe same client for colored diamondidentification and origin. Eachshowed an overall brown bodycolor,with concentrated color zones ofgreen or blue. In one diamond, a 1.80ct round brilliant, the concentrationof blue color was extremely notice-able in the face-up position. In theother stone, a 2.00 ct emerald cut, theblue-green zone was smaller and lessapparent in the face-up position.

When the emerald cut was exam-ined with magnification in diffusedlight, the blue-green color concentra-tion along the keel showed no sharpedges (as would be expected fromcyclotron irradiation), but there werealso no natural radiation stains any-where on the stone. While it is possi-ble to remove a radiation stain andnot the color beneath, a naturallyoccurring green-to-blue color is usual-

ly too shallow for the polisher toaccomplish this. Although the pres-ence of a GR1 center in the UV-visi-ble spectrum proved that the dia-mond had been exposed to ionizingradiation, it was difficult to seewhether the color zone followed thefacets, which would prove treatment(see Summer 1991 Gem Trade LabNotes, pp. 108–109). Consequently,we concluded that the origin of colorfor this diamond is currently undeter-minable.

In contrast, when we examinedthe 1.80 ct round brilliant in diffusedlight, it was obvious that the bluecolor zone at the culet followed thefaceted shape, a feature that can onlyresult from laboratory treatment.When we looked downward throughthe upper girdle facets (figure 3), theblue color was clearly visible and sep-arate from the brown color seenthroughout the body of the diamond.While it is not uncommon for browndiamonds to be irradiated (usually byan electron beam) to produce a strongblue-to-green color in the face-upposition, it appears that the originalbrown color of this stone was toostrong to be entirely masked.

TM and Thomas Gelb

Raman Analysis of InclusionsDuring a routine quality analysis, adiamond grader brought to our atten-tion an unusual inclusion in a 0.83 ct

marquise-cut diamond. The edge ofthe otherwise opaque, black-appear-ing, angular crystal inclusion appearedto have a brown “stain.” The graderthought the inclusion could be a dia-mond crystal with radiation burns onits surface; such stains would make iteasy to see, as diamond-in-diamondinclusions are generally invisiblebecause both have the same opticalproperties.

When the inclusion was examinedwith polarized light, its morphologyand apparent isotropic behavior onthin edges supported this preliminaryhypothesis. Because mineral inclu-sions in diamond often assume theisometric habit of the diamond host,however, the isometric appearance ofthis or any inclusion in a diamondcan be misleading. Furthermore, it isunlikely that an “included diamond”could show radiation stains on its sur-face, since the natural irradiation ofdiamond that forms such a “coating”is believed to be a post-growth phe-nomenon that occurs near the earth’ssurface.

A detailed microscopic examina-tion of this inclusion—with intensepinpoint fiber-optic illumination—revealed that the crystal actually hada dark red-brown color, which was

Figure 2. Before exposure to light, this 3.34 ct oval Maxixe-type berylwas dark blue (left). Eight hours of exposure in a solar simulator causedthis stone to fade considerably (right). The faded color is both less satu-rated and lighter in tone than the original, resulting in an appearancethat is both paler and grayer.

Figure 3. The concentration ofblue at the culet contrasts strong-ly with the brown bodycolor inthis 1.80 ct round brilliant dia-mond. Seen here through thecrown facets, color zoning thatclearly follows the faceted shapeof a diamond indicates a treatedcolor. Magnified 22¥.


clearly visible on thin edges. Themajority of the inclusion appeared tobe covered with an opaque blackmaterial that had a submetallic lusterand was bluish gray in reflected light(figure 4).

Because this inclusion was rela-tively close to the surface of the dia-mond, and the overlying facets werewell polished, we analyzed it by laserRaman microspectrometry. Wedetected weak signals for two differ-ent mineral components. To resolvethe inclusion data, the signal from thehost diamond had to be subtracted,which was done by setting the scanparameters to reduce sampling of thelarge diamond peak at 1334 cm-1.

Using this method, we identifiedthe opaque black material as graphiteand the dark red-brown areas aschromite. This suggests that themain mass of this inclusion ischromite, which was coated withgraphite. The conversion of diamondto graphite at the interface between amineral inclusion and its diamondhost is relatively well understood,and has even been reproduced in thelaboratory (see J. W. Harris and E. R.Vance, “Induced graphitisationaround crystalline inclusions in dia-mond,” Contributions to Mineralogyand Petrology, Vol. 35, 1972, pp.227–234). Graphitization is most like-ly responsible for most of the so-called “carbon spots” observed ingem-quality diamonds.

John I. Koivula

With Triangular “Void” InclusionsLast fall, a former staff member shareda 2.03 ct near-colorless oval-brilliant-cut diamond with staff members inthe East Coast lab because of itsunusual inclusion pattern (figure 5): agroup of “internal trigons” that wereall oriented in the same direction andapparently aligned along an octahedralplane. This inclusion scene was rem-iniscent of a triangular arrangementof numerous triangular voids seen ina 1.74 ct marquise cut diamond thatwas reported in the Spring 1995 GemTrade Lab Notes (p. 53).

Careful examination of this inclu-sion formation indicates that, justlike the inclusion pattern previouslyreported, it represents a phantomoctahedral crystal face that is invisi-ble except where decorated by thenumerous tiny, flat triangular voidsthat formed along a growth interface.

Even though these individual tri-angles are transparent, their highrelief and almost silvery metallic lus-ter suggest that they are “voids.”Since no cleavage planes or fractureslink them to the surface of the hostdiamond, it is probable that they con-tain a gas or fluid that was trappedand sealed off during growth. Tinycleavage “halos” were seen at theedges of some of the triangles. Theseminute cracks might have resultedfrom a large difference in pressurebetween the conditions present whenthe inclusions formed, and thosewhen the diamond was emplaced in

the transporting magma; stressinduced during mining and facetingmight also have caused the cracks.

John I. Koivula

SYNTHETIC DIAMOND, Showing Change of Color

This past fall, a client showed a mostinteresting synthetic diamond to thelaboratories on both coasts. Althoughthe 0.51 ct round brilliant appearedmostly brown (due to both a darktone and low saturation), it exhibiteda color change from a greenish yellowhue in day (or fluorescent) light to anorange hue in incandescent light, asshown in figure 6. This first stone wasproduced by accident, but the manu-facturer has since reproduced the phe-nomenon in several more syntheticdiamonds.

The round brilliant was readilyidentified as synthetic diamond bystandard gemological testing.Magnification showed a cloud of pin-points in the form of a square underthe table, as well as several tiny grayinclusions. Brown graining alongcubic directions formed a long, slimhourglass shape in profile view, andsome of this graining luminescedgreen to strong visible light. Whenviewed with the long-wave UV lamp,this same brown graining fluorescedyellowish green, which was visiblethrough the table as a cross pattern.When exposed to short-wave UV, thebody of the stone fluoresced a weakorange, and the green cross persisted.Unlike the colored synthetic dia-monds we reported on previously,this one showed a strain pattern(anomalous birefringence) that fol-lowed the cubic graining.

Several spectral features indicatedthat this synthetic diamond had beentreated after growth. The infraredspectrum revealed a type IaA dia-mond, rather than the type Ib thatmost yellow synthetic diamonds are.Also present were clear, moderate-sized H1a and H1b bands (at 1450 and4935 cm-1, respectively), which areknown to develop following irradia-tion and heating (A.T. Collins et al.,

Figure 4. This inclusion in dia-mond was identified by Ramananalysis as chromite that is coatedwith graphite. Magnified 63¥.

Figure 5. Numerous triangularvoids decorate a phantom octa-hedral face in this 2.03 ct dia-mond. Magnified 63¥.


“Spectroscopic studies of the H1b andH1c absorption lines in irradiated,annealed type Ia diamonds,” Journalof Physics C: Solid State Physics, Vol.19, 1986, pp. 3933–3944). The infraredspectrum also showed weak absorp-tions due to hydrogen, an impuritypreviously unreported in syntheticdiamond.

The visible spectrum showed awell-developed N-V center, with aprimary peak at 637 nm and relatedabsorptions at 503, 575, and 594 nm.While this center occurs rarely innatural-color diamonds, it is com-monly found in those that have beenirradiated and heated, most notablytreated-color pink to purple dia-monds. Although there are someother peaks in the spectrum, thisbroad feature between about 550 and637 nm, along with the transmissionregions on either side, causes thecolor-change behavior. (For an expla-nation of the color-change phe-nomenon, see Y. Liu et al., “The‘alexandrite effect’ in gemstones,”Color Research and Applications,Vol. 19, No. 3, 1994, pp. 186–191.)

IR

PEARLS

Cultured, with a Faceted SurfaceAnother interesting item that theEast Coast laboratory received for

identification was a strand of 10–13mm light gray cultured pearls thathad been fashioned in a most unusualway: All were completely covered byrhombic facets, which gave them adistinct “polished” appearance (figure7). We had seen similar culturedpearls at the 1997 Tucson gem andmineral shows, as reported in theSummer 1997 Gem News (pp.146–147).

The X-radiograph substantiatedthat these were cultured pearls. Whenwe examined them with long-waveultraviolet radiation, however, wenoticed an uneven greenish yellowfluorescence, which was more intensealong the facet edges. With magnifica-tion, it became evident that all facetswere indeed flat and showed verysharp edges. They were completelysmooth and had a mirror-like appear-ance in reflected light; we saw nopolishing lines. The characteristicgrowth or suture lines in the nacre,formed by the edges of the overlap-ping aragonite platelets, were barelyvisible: They appeared as very faintlines rather than as narrow grooves.This overall flatness of the surfacegreatly increased the observed luster.

We also noted that carefullyapplied pressure from the tip of a nee-dle probe left smooth indentations onthe surface of the cultured pearl, simi-lar in appearance to those depressionsleft on a coated surface. This responsemay be a result of the extremesmoothness of the polished face,residue left on the surface from pol-ishing, or a superficial coating appliedafter polishing. KH

Figure 6. Beneath the overall brown color, this 0.51 ct synthetic dia-mond shows a color change from a greenish yellow hue in daylight (left)to an orange hue in incandescent light (right).

Figure 7. The faceted surfaces of these 33 cultured pearls (10 –13 mm indiameter) were extremely flat and showed very high luster.


Non-Nacreous “Pearls”By coincidence, last summer our labo-ratories on both coasts received twogroups of symmetrical, oval- to drop-shaped, light pink concretions forexamination. Some specimens wereevenly colored, but others showedslight color variations (mainly darkerbands of color encircling them). Themost prominent feature was a “mosa-ic” pattern that covered the entiresurface and gave rise to a sheen-likeeffect in reflected light (figure 8).

This appearance reminded us ofthe flame-like pattern seen in someconch “pearls.” The sample in figure8 is particularly attractive, an ovalshape that measured approximately14 ¥ 12 mm in diameter. With 10¥magnification, the surface looked fair-ly smooth. There were no signs of anypolishing lines that might indicatethat the specimen had been cut andpolished to produce its shape.Standard testing verified that thespecimen was a carbonate.

An X-radiograph revealed a homo-geneous structure, which proved thatthe specimen was indeed a naturalconcretion. The surface of the pearl(figure 9) showed a pattern of denselypacked polygons, which indicate aradiating prismatic structure; thepolygons are cross-sections of the car-bonate prisms. According to consult-

ing biologist Dr. C. Hedegaard, thisgeometry contrasts with the stackedshingles of nacre tablets found incommon pearls, as well as with theflame-like pattern in pearl formationswith crossed lamellar structure (e.g.,Melo melo and Strombus gigas [conch“pearls”]). To our knowledge, variousthorny oysters can produce concre-tions (see Winter 1987 Gem TradeLab Notes, p. 235). Our clientinformed us that this unusual concre-tion came from an oyster found alongthe Pacific Coast of North America.

KH

SPINEL, with a Darker Core

When you mention high-quality natu-ral red spinel to anyone in the gem orjewelry trade, they usually think ofBurma (now Myanmar) as a localityand often, more specifically, of theMogok region. This is because naturehas seen fit to have its finest redspinels “walk hand-in-hand” with itsfinest rubies in this locality.

In fact, spinel is commonly associ-ated with ruby in many gem depositsworldwide. These two gems are closechemical cousins with a similar para-genesis, and in both cases the redcolor is caused by chromium.However, whereas ruby from Mogokis known for its distinctive roiled or

heat-wave-like color zoning, the redspinels from this area (and spinels ingeneral) do not commonly exhibitcolor zoning.

It was, therefore, with great inter-est that we saw distinct color zoningin a 1.11 ct oval mixed-cut red spinelfrom Mogok (figure 10). The colorzoning was not apparent when thisgem was examined without magnifi-cation; rather it appeared to have auniform color, as would be expectedin a fine spinel. With magnificationand standard, darkfield illumination,the color also appeared even. The nat-ural origin of this stone was immedi-ately discernible by the presence ofnumerous small negative crystals andbirefringent mineral inclusions.These crystals appeared to outlineone half of an octahedral “phantom”or core which was also delineated byedges that were somewhat rounded ormelted looking.

Another interesting feature of thisstone was its refractive index. Whentesting spinel, one generally expectsto get a single consistent reading.With this gem, however, the R.I.obtained from the table was 1.732,while testing anywhere else on thecrown or pavilion gave a reading of1.718. Such a variation could easilylead to the erroneous conclusion thatthe stone was assembled. Since mostflame-fusion synthetic spinel isknown to have an R.I. of about 1.73,

Figure 8. Note the color bandsencircling one end of this 14 ¥12 mm calcareous concretion,which was produced by anoyster from the Pacific Coastof North America.

Figure 9. A closer look at theuneven coloration of the “pearl”in figure 8 shows the radiatingprismatic structure of the car-bonate grains of which it is com-posed. Magnified 12¥.

Figure 10. This 1.11 ct spinelfrom Myanmar appears evenlycolored face up, but it is actual-ly strongly color zoned andshows two different refractiveindex readings.


and since most natural spinel gives asingle refractive index reading ofabout 1.71 to 1.72, the double readingon this stone could lead one toassume that the table area was com-posed of synthetic spinel, while thepavilion area was natural.

Given the unusual resultsobtained with both magnification andthe refractometer, we decided toexamine the stone further usingimmersion in methylene iodide anddiffused transmitted light. The colorzoning became obvious (figure 11), inthe form of a deep red, diamond-shaped core that was surrounded bymuch lighter pink spinel. The stonewas then rotated for a profile view ofthe centralized color zone (again, seefigure 11), which was revealed to be ahalf-octahedron with a large portionexposed on the surface of the tablefacet. It was now clear that the redcore had the higher refractive index of1.732, while the pink areas had theslightly lower index expected for nat-ural spinel.

Since the properties of this spinelwere so unusual, we explored thechemical composition of the samplewith energy-dispersive X-ray fluores-cence (EDXRF) analysis. Althoughour instrumentation is not calibratedto give quantitative results for spinel,this method can show if there is moreof a particular element(s) on one sur-face of a faceted stone or crystal thanon another. Mike Moon of GIAResearch measured significantly more

chromium and vanadium on the tablefacet, where the red octahedral phan-tom core was exposed to the surface,than on the pavilion.

As a last test, we performed laserRaman microspectrometry on boththe table and pavilion surfaces. Whilethe instrument identified both testareas as spinel, the peaks obtainedfrom the darker red table were 50%higher (i.e., more intense) than thosegenerated from the pavilion. Like theobvious differences in refractive indexrecorded for this stone, this is appar-ently the result of the greateramounts of chromium and vanadiumin the darker red core exposed on thetable surface.

This is not where the story ends.Last September, Mike and Pat Gray ofGraystone Enterprises in Missoula,Montana, showed this writer a parcelof small, transparent, bright red “cut-ting rough” spinel octahedra fromMyanmar. Microscopic examinationof two of these crystals (0.19 and 0.20ct) revealed distinct, rounded cores ofa deeper red color. The low relief ofthese cores showed that they werevery close in refractive index to thesurrounding spinel. It was only thestrong difference in color that madethem readily visible. Another 0.20 ctspinel crystal from this group showedwhat appeared to be an oblong coresurrounded by layers of roiled growthzoning (figure 12), which is more rem-iniscent of what we expect to see inMogok rubies.

Since the darker red cores of thetwo samples seemed to blend into thesurrounding crystals with no sign ofan interfacial separation—and, unlikethe first spinel described above, thecores were not exposed on the surfaceof either crystal—we used a Beckeline method (see. e.g., W.D. Nesse,Introduction to Optical Mineralogy,Oxford University Press, New York,1991, pp. 26–30) to determine thatthe cores had a higher refractive indexthan their host.

It is not known how unusual suchcolor-zoned red spinels are. In the par-cel of 48 small octahedra, just twowith darker red cores were found withmagnification alone. Since immersionis not generally used as a testing pro-cedure in the identification of spinel,the color zoning in such stones couldeasily be overlooked by a less-experi-enced gemologist. Yet knowledge ofsuch a core could help the cutter pro-duce a darker red stone.

John I. Koivula

PHOTO CREDITSMaha DeMaggio took photos 1, 2, 6, 8, and 10.Vincent Cracco provided figures 3, 4, and 5.Nicholas DelRe photographed figure 7. JohnKoivula was the photographer for figures 9 and11–12.

Figure 11. Immersion in methylene iodide revealed strong color zon-ing (left) in this 1.11 ct natural spinel. The profile view (right) showsthat the dark red zone (6.82 mm long) is exposed on the surface ofthe table facet.

Figure 12. The strong roiledgrowth zoning around theoblong core in this 0.20 ct redspinel is unusual in spinel, butsimilar to that seen in Mogokrubies. Magnified 25¥.

290 Gem News GEMS & GEMOLOGY Winter 1998

DIAMONDS

Diamond production starts at Canada’s Ekati mine.October 14, 1998, marked the opening of the Ekati dia-mond mine in Canada’s Northwest Territories (NWT).About 125 guests attended the event, including ministersfrom both the federal and territorial governments, offi-cials of indigenous peoples’ groups and municipal gov-ernments, executives of several mining companies, andmedia representatives. Prof. A. A. Levinson (Universityof Calgary, Alberta) attended on behalf of Gems &Gemology and provided the following report.

Several large mining companies began exploring fordiamonds in the NWT in the early 1980s, but by 1985most had withdrawn from the area. However, the inde-fatigable Charles E. Fipke, who in 1983 incorporated DiaMet Minerals Ltd., continued the arduous and expensiveexploration along with his partner, Stewart L. Blusson. In1985, Fipke found the first diamond indicator minerals(most importantly, “G10” pyrope garnets) in glacialdeposits in the vicinity of Lac de Gras (figure 1). Hestaked the first claims for diamonds in the NWT in 1989.In September 1990, Dia Met and BHP Minerals (a sub-sidiary of Australia-based Broken Hill Proprietary Ltd.)signed a joint-venture agreement for the NWT DiamondsProject; BHP became operator of the project.

Within a few months, the joint venture had located alikely source of the diamond indicator minerals (whichnow included chrome diopside) under what was subse-quently named Point Lake. Following geophysical sur-

Figure 1. Five kimberlite pipes make up the Ekati dia-mond mine, which is located about 300 km northeastof Yellowknife in the Northwest Territories. Artworkmodified from original provided by Outcrop; courtesyof BHP Diamonds Inc.

Gem News GEMS & GEMOLOGY Winter 1998 291

veys, in spring 1991 a core hole was drilled under PointLake and the first diamond-bearing kimberlite pipe wasconfirmed (it is presently noneconomic, at a grade of 0.6ct/tonne with diamonds valued at less than US$40/ct).To date, the joint venture has discovered more than 100kimberlite pipes, many of which contain diamonds,within its 1,820 km2 stake on the north side of Lac deGras. The economic potential of some of the pipes hasyet to be determined. The five kimberlite pipes that nowcomprise the Ekati diamond mine, in order of their dis-covery between 1992 and 1995, are Fox, Koala, Misery,Panda, and Sable (again, see figure 1).

Most of the pipes are located under lakes that formedbecause the kimberlite was eroded more easily than thesurrounding granite by advancing glaciers during the lastIce Age. By world standards, these kimberlite pipes aresmall (e.g., Panda is about 3 ha [hectares], or 7.4 acres),but they can have extremely high grades and/or high val-ues (table 1 and figure 2). (Most kimberlite mines operat-ing today are larger than 6 ha. For example, Mir is 6.9 ha,Venetia is 12.7 ha, and Premier is 32.2 ha.)

By late 1993, it was clear to the joint venture that aviable diamond mine could be developed in the Lac deGras region. In 1994, BHP Minerals transferred its inter-est to BHP Diamonds Inc., a newly formed Canadian cor-poration. In December of that year, BHP Diamonds Inc.notified the Canadian government of its intent to minethe deposit. However, the mine is located in an area ofcontinuous permafrost, with a fragile ecosystem. In July

1995, an extensive environmental impact study was sub-mitted for government review. Following a careful evalu-ation, the successful conclusion of negotiations with fourindigenous peoples’ groups, and approval by the FederalCabinet, all necessary licenses and permits wereobtained by January 1997, allowing construction tobegin. Close attention was paid to integrating the projectwith the local communities and the economy of theNWT (for example, about 550 permanent jobs have beencreated, 30% of which are held by indigenous people.)

The project was named Ekati in 1997, with the own-ership distributed as follows: BHP Diamonds Inc. (51%),Dia Met Minerals Ltd. (29%), Charles E. Fipke (10%), andStewart L. Blusson (10%). Ekati means “fat lake” and isthe name traditionally used by indigenous people for Lacde Gras. It refers to the white quartz rock found in abun-dance around the lake, which resembles caribou fat.

Construction of the mine presented numerous chal-lenges because of the remoteness of the area, the lack ofpermanent roads (a 475 km ice road is available fromYellowknife, the territorial capital, for only 8–10 weeksfrom mid-January to mid-April), the lack of other types ofinfrastructure (e.g., electricity), and the harsh climate(temperatures can drop to -50°C in the winter months).Yet construction of a processing plant and supportingfacilities, as well as preparation of the first kimberlite formining (Panda; see figure 3), were completed on schedulein 21 months. This is an amazing engineering and logisti-cal feat, considering the difficulties mentioned above. Sofar the investment in Ekati totals about US$700 million.

The five kimberlites at Ekati will be mined in asequence determined by the size and location of eachpipe, as well as by the projected value of (and marketdemand for) the diamonds they contain. This plan isdesigned to provide a consistent production, both byquality and value of the diamonds. Some ore will bestockpiled in case mining is interrupted by equipment

Figure 2. All of these diamonds were recovered fromthe Ekati mine. (The largest rough diamond reportedthus far weighed 47 ct, but we do not know if it wasgem quality.) Photo courtesy of BHP Diamonds Inc.

TABLE 1. Ore reserves and the timetable (anticipatedproduction dates) for mining diamonds at the five pipes comprising the Ekati diamond mine.a

Panda Misery Koala Sable Fox

1998– 1999– 2002– 2007– 2008– Total (T )Production 2009 2013 2013 2013 2015 Avg. (A)

Mining reserves 13.4 5.5 17.4 12.9 16.7 66.0 (T )(millions of tonnes)b

Grade of kimberlite 1.09c 4.26 0.76d 0.93 0.40 1.09 (A)(ct/tonne)Average value of 130 26 122 64 125 84 (A)diamonds (US$/ct)

a Production schedules are subject to change. All pipes will bemined initially by open-pit methods. Underground mining will occurlater at the Panda and Koala pipes. Modified from Dia Met MineralsLtd. Annual Report 1997-1998. A particular year (e.g., 1999) refersto the fiscal year, which starts in June (e.g., June 1999–May 2000).

b Includes both proven reserves (43.5 million tonnes total) and probablereserves (22.4 million tonnes total); 1 tonne = 1,000 kg = 2,204.6pounds (avdp).

c Grade includes the 0.97 ct/tonne material in the underground mining portion of 2.8 million tonnes.

d Grade includes the 1.63 ct/tonne material in the undergroundmining portion of 0.8 million tonnes.


breakdown or extreme weather. Production from Ekati,initially only from the Panda pipe, is scheduled at 9,000tonnes of kimberlite per day, yielding approximately10,000 carats of diamonds daily (about enough to fill alarge coffee can). Annually this is equivalent to 3.5–4.5Mct (million carats) of rough gem and industrial dia-monds, worth about US$500 million. On the basis ofcurrent world production (115 Mct), this will constituteabout 4% of the total annual supply by weight and 6%by value. It is planned that, after 10 years, productionwill be increased to 18,000 tonnes of kimberlite per day,requiring an additional investment of US$80 million.Over the initial 17 year life of the Ekati mine, about 66million tonnes of ore will be processed from the fivekimberlite pipes (again, see table 1), yielding about 72Mct of diamonds (based on an overall grade of 1.09ct/tonne). In view of the numerous other kimberlites inthe area, some of which almost certainly will be minedin the future, mining in this region is expected to last forat least 25 years.

The rough diamonds will be sorted and evaluated at aspecially designed facility near the Yellowknife airport,beginning in early 1999. Initially, all of the rough dia-

monds will be exported to Belgium, to be marketedthrough BHP Diamonds’ sales office in Antwerp, withthe assistance of I.D.H. Diamonds NV. It is anticipatedthat a limited number of cutting facilities eventually willbe established in various parts of Canada.

Ekati is the first of what are likely to be several newdiamond mines in Canada. The Diavik project, whichborders Ekati on the south, is being developed by RioTinto PLC and Aber Resources; it is expected to beginproduction in 2002 with about 6 Mct annually. When theDiavik production is combined with that of Ekati, about10% of the world’s diamonds (by both weight and value)could come from Canada; this is comparable to currentproduction from South Africa.

Financial Times Diamond Conference. Gems &Gemology editor Alice Keller attended this one-day con-ference, which was held in Antwerp, Belgium, onOctober 28. Three main areas of the diamond businesswere addressed: supply, manufacture, and demand.

De Beers has a major stockpile of diamonds (whichthey valued at about $4.6 billion as of June 1998) and canadjust supplies to assure stability for rough diamondprices. Given concerns about diamond demand (seebelow), the Central Selling Organisation (CSO) will con-tinue to restrict sights, and not all sightholders willreceive diamonds at each one. The main sources forstones outside CSO marketing channels have beenRussia, Angola, and Australia; Canada is now poised as afourth source. Despite its own economic crisis, Russia isin a good position to continue diamond mining; however,production is not likely to increase in the near future,and current production is completely absorbed by theCSO and the Russian cutting industry. Mining in Angolais uncertain (and expensive) because of the civil war rag-ing there, which shows no sign of abating. However,Angola has produced several million carats of alluvialstones in recent years, and the first kimberlite pipe to bemined there, Catoca, recovered more than 122,000 caratsin one month in 1998. Although Canada’s Ekati minewill produce about 3.5–4.5 Mct annually, with no plansby BHP to stockpile goods, De Beers’s representatives donot believe that Canadian production will have a signifi-cant impact on supply.

Two related economic problems bedevil manufactur-ers: overcapacity and financial liquidity. Today, the dia-mond industry is in transition from being supply drivento being demand/marketing driven. India is now theworld’s leading diamond manufacturer, producing 9 ofevery 10 fashioned diamonds, with costs as low as $0.75to cut a small sawn stone. The huge manufacturingcapacity there has led to excess inventory. Israel is suffer-ing because so much of their business fed demand inAsia. Rough imports to New York decreased 23% for1997 compared to 1994, yet diamond jewelry sales in theU.S. continue to rise. However, this increased demand is

Figure 3. This aerial photograph of the Ekati diamondmine, looking south (with the camp and processing

facilities in the distance), was taken in August 1998.The Panda pit (foreground) measures about 900 m in

diameter; the kimberlite is the much smaller darkregion in the center and lower right of the pit floor. (The

area of the pit is larger than the pipe because of therequirements of open-pit mining.) Eventually, the bot-

tom of the pit will be about 100 m wide and 300 mbelow the present surface, at which time underground

mining will commence. Just beyond the Panda pit isKoala Lake, which marks the location of another kim-

berlite that is scheduled to begin mining in 2002. Photo ©Jiri Hermann/BHP Diamonds Inc.


primarily for less-expensive goods, rather than for themore important stones cut in New York. Like Israel andNew York, the Belgian diamond industry must contendwith high wages relative to India. Recent allegations thatdrug dealers are laundering money through the Antwerpdiamond trade may lead to further scrutiny on the part ofgovernment authorities.

Diamonds have been adversely affected on thedemand side, not only because of the Asian financial cri-sis, but also because consumers in Japan appear to beputting disposable income into goods other than dia-monds. (In Japan, diamonds—especially solitaire ringswith certificates—are perceived to be the least profitablepart of a jeweler’s inventory.) More and more diamondmanufacturers look to U.S. consumers to compensate forlost Asian sales. The auction market saw a recent drop indemand: Christie’s sold only 50% of the lots offered at itsOctober 1998 sale in New York, and the companyresponded immediately with a reduced, more selective,December auction. One key to building demand is adver-tising; in addition to its own branding initiative (stillbeing “test-marketed”), De Beers continues to invest$200 million per annum in “generic” diamond advertis-ing worldwide. Overall, technology is altering the “dia-mond landscape”: improved communications (e.g., theInternet), new instruments, and ongoing research arechanging the way diamonds are found, fashioned, andregarded.

COLORED STONES

Colored stone presentations at the InternationalMineralogical Association meeting. The Fall 1998 GemNews section reported the results of several diamondinvestigations described at the 17th IMA meeting inToronto, Ontario, last August. There were also numer-ous presentations on colored stones, several of which aresummarized below.

George Rossman (California Institute of Technology,

Pasadena) delivered a plenary lecture on the origin ofcolor in minerals. The coloration of tourmaline, garnet,and the colored varieties of quartz are due to transitionmetal ions (often interacting to produce different colors)and microscopic inclusions. Color also can be inducedwhen natural background radiation changes the oxida-tion state of ionic impurities. D. C. Grenadine (SlipperyRock University, Pennsylvania) attributed the formationof the color centers that produce yellow to brown in sili-cate minerals such as quartz, topaz, and beryl, to ionicimpurities in the presence of aluminum that has substi-tuted for silicon in tetrahedral sites. In two presentations,John Emmett and Troy Douthit (Crystal Chemistry,Brush Prairie, Washington) described the techniques usedto treat some gemstones (especially sapphire), which mayresult in a substantial improvement in color and/or clari-ty (see, e.g., figure 4) and therefore value.

There were numerous presentations on gem corun-dum. F. L. Sutherland (Australian Museum, Sydney) pre-sented a model for the origin of two geochemically dis-tinct suites of corundum from alkali basalts, wherebypartial melting of the lithosphere over a rising plume ofthe earth’s mantle can lead to repeated eruptions ofpotentially gem-bearing lava. M. I. Garland and col-leagues (University of Toronto) inferred that the alluvialsapphires from southwest Montana came from a crustalmetamorphic source, on the basis of their relatively low(40–60 ppm) gallium contents. T. Häger (University ofMainz, Germany) and colleagues studied the trace-ele-ment chemistry and inclusions in rubies from two min-ing areas in Vietnam—Luc Yen (where the rubies are pro-duced by metasomatic processes in marble) and QuyChau (where pegmatites introduced into sillimanite-bearing schists are responsible for ruby formation). T.Häger also studied the cause of color in sapphire, andnoted that magnesium seemed to be required (as well asFe and Ti) to explain the coloration of heat-treated yel-low sapphire. D. Tang (University of Fuzhou, Fujian,China) attributed the blue color of sapphires from Mingxi

Figure 4. Some near-colorless geuda sapphires from Sri Lanka (left) become commercially importantafter heat treatment improves their color (right). The stones range from 1 to 4 ct. Photos courtesy ofJohn Emmett, Brush Prairie, Washington.


(Fujian Province) to a defect cluster containing hydrogenas well as iron and titanium. A. V. Lyutin (Moscow StateUniversity, Russia) and colleagues grew flux syntheticrubies with up to 6.38 wt.% Cr2O3 from PbO-V2O5-WO3

flux. They found that samples grown in this flux, and inLi2O-WO3 flux, at 1100°–1250°C, had rather equidimen-sional shapes.

I. I. Moroz (Hebrew University of Jerusalem, Israel)and G. Panczer (University Claude Bernard, Lyon,France) examined the Raman spectra of emeralds fromseveral deposits, and suggested that this technique mightsomeday be useful to differentiate emerald localities. I. Z.Eliezri (Colgem Ltd., Ramat Gan, Israel) and I. I. Morozexamined the compositions of mica and talc inclusionsin emeralds from different sources, and likewise suggest-ed that these compositions might be useful to identifyemerald sources. G. Graziani (University of Rome “LaSapienza,” Italy) used infrared spectroscopy to investigateseveral possible sources for ancient Roman emeralds.

A. M. R. Neiva (University of Coimbra, Portugal) andco-workers described the trace-element chemistry ofblue, green, pink, and white beryl from Namivo, AltoLigonha, Mozambique. Z. L. Li and colleagues (Zhong-shan University and Nanjing University, China) charac-terized zinc spinel and other daughter crystals found in

melt inclusions in pegmatite beryl from Xinjiang,Hunan, and Yunnan Provinces, China. J. M. Evenson(University of Oklahoma, Norman) and colleagueslooked at the equilibrium among beryl, aluminosilicates,chrysoberyl, and quartz in an aluminum-rich graniticmelt; they found that beryl could crystallize at very lowberyllium concentrations in low-temperature-solidifyingmelts.

T. Lu (GIA Research, Carlsbad) and colleaguesdescribed differences between natural and syntheticamethyst, citrine, and ametrine. Some syntheticamethyst can be identified by the orientation of colorzones and growth bands, pleochroism, and a characteris-tic IR absorption peak at 3540 cm-1. I. K. Bonev(Bulgarian Academy of Science, Sofia) suggested that thinmicroscopic calcite plates acted as seeds for well-formedcrystals of “fadenquartz” (quartz crystals containingopaque white strips that might be mistaken for the seedplates in synthetic quartz), which form in Alpine-cleft-type deposits in Switzerland and elsewhere.

Advanced analytical techniques were described inmany presentations. M. Gaft (Open University of Israel,Tel Aviv) and G. Panczer illustrated the use of laser-induced time-resolved luminescence spectroscopy to dif-ferentiate among luminescence centers with similaremission spectra but different decay times; previouslyunknown causes of luminescence (mostly involving rare-earth elements) were documented. M. Superchi and E.Gambini (CISGEM, Milan Chamber of Commerce, Italy)discussed the use of infrared spectrophotometry, energy-dispersive spectrometry, and Raman microspectrometryto identify treatments and differentiate between varietiesof organic and amorphous gem materials. A. Banerjee(University of Mainz, Germany) and D. Habermann(Bochum University, Germany) used hot-cathodecathodoluminescence to differentiate between naturaland cultured freshwater pearls from North America andChina, respectively. P. Zecchini (University of Franche-Comté, Besançon, France) and colleagues usedreflectance IR spectroscopy, electron microprobe analy-sis, and X-ray diffraction to determine nondestructivelythe species, composition, and lattice parameters of gemgarnets.

Gem-bearing pegmatites were highlighted by severalresearchers. K. L. Webber and colleagues (University ofNew Orleans, Louisiana) calculated the crystallizationtimes of some gem-bearing pegmatites in San DiegoCounty, California; for the famous Himalaya dike atMesa Grande, they estimated that the pegmatite cooledto 400°C in only five to 14 days. P. Keller (University ofStuttgart, Germany) defined several belts of rare-elementpegmatites in Namibia’s Central Damara Province; gemtourmaline has been found in some of these pegmatites.B. M. Laurs (GIA Gems & Gemology) surveyed the gem-stone resources and the geologic setting of kunzite-elbaite-beryl pegmatites in Afghanistan (see, e.g., figure5), and suggested possibilities for further exploration. A.

Figure 5. Granitic pegmatites in Afghanistan arerenowned for producing large quantities of gem-qual-ity spodumene in a variety of colors. This kunzitecrystal is 11.8 cm long. Courtesy of Bill Larson,Fallbrook, California; photo © Jeff Scovil.


B. Rao and M. S. Adusumilli (University of Brasilia,Brazil) gave exploration guidelines for aquamarine- andelbaite-bearing pegmatites in Borborema Province, RioGrande do Norte, Brazil. C. Kasipathi (AndhraUniversity, India) and A. B. Rao described the sourcerocks (mostly pegmatites) for many gems (e.g., ruby,alexandrite, tourmaline, topaz, and garnet) in theKhammam, East Godavari, and Visakhapatnam districtsof Andhra Pradesh State, India.

Chalcedony with goethite inclusions from Madagascar.On a recent trip to Madagascar, Michel Bricaud of LaRose du Désert, Bagneux, France, acquired a largequantity of an unusual variety of chalcedony (figure 6),some of which was examined by Gem News contribut-ing editor Emmanuel Fritsch at the University of Nantes,France. The material is currently being fashioned intocabochons.

The chalcedony contains abundant tiny, dark spheri-cal aggregates, typically 0.1– 0.2 mm in diameter. Theirdark brown color contrasts sharply with the white orbeige of the matrix, and their small size creates very finedetail in the inclusion patterns. With magnification,these spherules show yellow-brown internal reflections,which suggests that they are goethite.

Chemical analyses of the spherules were performedwith a JEOL 5800 LV scanning electron microscope,equipped with an energy-dispersive detector that candetect most light elements, including oxygen (but not,e.g., hydrogen). The only elements detected by SEM-EDXwere iron and oxygen, as well as small amounts of sili-con from the chalcedony matrix. This chemistry is typi-cal of iron oxides and hydroxides. X-ray diffraction analy-sis of a fragment of chalcedony particularly rich in theinclusions showed peaks corresponding to goethite, inaddition to the quartz peaks. Dr. Fritsch therefore identi-

fied the small brown spherules as goethite [a-FeO(OH)]inclusions in chalcedony.

Iolite gemologically indistinguishable from feldspar. Thevast majority of gem identifications today—well over90%—can still be made with the standard methods avail-able to most gemologists and jewelers. However, occa-sionally we receive gem materials that present especiallysubtle challenges. The actual identities of these materialsoften are not even suspected unless so-called advancedtesting techniques are used. One example was thefaceted genthelvite described in the Fall 1995 Gem News(pp. 206–207), which could not be distinguished from(much more common) pyrope-almandine garnet usingstandard gem-testing methods.

Recently, we were asked to look at a colorless, trans-parent oval mixed cut (figure 7), which weighed 1.48 ctand measured 9.31 ¥ 7.09 ¥ 4.05 mm. The stone was ini-tially represented to K & K International of Falls Church,Virginia, as oligoclase feldspar from Sri Lanka. Thegemological properties of this stone were typical for pla-gioclase feldspar in the albite-oligoclase compositionalrange. Its three refractive indices were a =1.531, b =1.534, and g = 1.541, yielding a birefringence of 0.010.The optic character and sign were biaxial positive. Thespecific gravity, as determined hydrostatically, was 2.62(average of three measurements). The stone was inert toboth long- and short-wave UV radiation. When it wasviewed with a microscope in polarized light, lamellartwinning was obvious (figure 8); this feature was similarto that commonly seen in plagioclase.

To confirm the stone’s identity, we analyzed it withthe laser Raman microspectrometer. We were surprisedwhen the Raman spectrum indicated that this colorless

Figure 6. The tiny black inclusions forming finepatterns in these chalcedony samples fromMadagascar (each about 4 cm across) were iden-tified as goethite. Photo by A. Cossard.

Figure 7. At first, this 1.48 ct colorless iolite wasthought to be feldspar. The 18.49 ct iolite blockshown on the left was used as a reference standardfor Raman analysis. Photo by Maha DeMaggio.


gem was cordierite (iolite). Three different areas of thestone were tested, all with the same result. To corrobo-rate this identification, we performed Raman analysis onan 18.49 ct rectangular block of blue iolite (also shown infigure 7). On the basis of the results obtained, there is noquestion that the colorless stone is cordierite and not afeldspar, even though the gemological properties of thisstone would be consistent with either gem material.

Although lamellar or polysynthetic twinning ofcordierite is not mentioned in gemological texts, miner-alogy texts do list this structural property as a commonfeature. For example: “Cordierite may show polysynthet-ic twinning and birefringence resembling that of plagio-clase” (W. R. Phillips and D. T. Griffen, OpticalMineralogy, the Nonopaque Minerals, 1981, W. H.Freeman and Co., San Francisco, p. 168). In fact, the blueiolite sample that we used as a Raman standard alsoshowed excellent twinning in polarized light (figure 9).

Because plagioclase and cordierite have similar gemo-logical properties, it is quite possible that these gemscould be misidentified, especially samples from a localitythat hosts both gem minerals (e.g., Sri Lanka, India, andMadagascar).

New features of Montana sapphires: Gold is where youfind it. Since 1992, Marc Bielenberg of Hamilton,Montana, has been involved in an extensive sapphiresampling project on the main drainage and both forks ofMontana’s Dry Cottonwood Gulch. Those gem-quality,water-worn crystals that were deemed suitable for heattreatment were visually separated from the “rejects,”

Figure 9. Areas of polysynthetic twinning were alsoobserved in the iolite block shown in figure 7.Photomicrograph by John I. Koivula; polarized light,magnified 20¥.

Figure 10. Rounded, metallic grains of pyrrhotite aresurrounded by decrepitation halos in this sapphirefrom Dry Cottonwood Creek, Montana.Photomicrograph by John I. Koivula; magnified 25¥.

Figure 11. This crystal of clinozoisite in sapphirefrom Dry Cottonwood Creek displays perfect cleav-age; it also hosts a smaller unidentified rod-shapedinclusion. Photomicrograph by John I. Koivula;magnified 35¥.

Figure 8. In polarizedlight, the colorlessiolite showed obviouspolysynthetic twin-ning. These two viewsillustrate the sampleat slightly differentorientations.Photomicrographs byJohn I. Koivula.


which were mostly smaller stones of apparent lowerquality. These reject stones were stored for several yearswithout any further examination.

During the 1997–1998 winter season, when miningactivity had ceased, Mr. Bielenberg decided to examinethe reject sapphires more closely. While searching forinteresting or unusual inclusions, he discovered whatlater were proved to be (by Raman analysis and X-raypowder diffraction) mineral inclusions of pyrrhotite (fig-ure 10) and clinozoisite (figure 11), which were not previ-ously known as inclusions in Montana sapphires.

A real surprise, however, was the discovery of micro-scopic grains of gold in the crevices, pits, and cracks ofsome of these sapphires. The gold had the form of tinywater-worn nuggets (figure 12) rather than flakes. In noinstance was gold observed as an actual inclusion in anyof these sapphires. Mr. Bielenberg observed gold on thesurfaces of 135 of the 600–700 stones he examined. Mostof these stones had only one microscopic nugget; themost gold particles found on any one stone was four.Higher magnification shows that, at least in someinstances, the gold appears to have been smeared by fric-tion across the surface and into cracks and crevices(inset, figure 12). To confirm the identification, energy-dispersive X-ray fluorescence analysis by SamMuhlmeister of GIA Research resolved a gold peak fromeach of two different sapphires.

Because the gold can be removed from the surface ofthe sapphires with a small probe, it is evident that thegrains are not strongly bonded to the sapphires.Apparently, the gold was naturally wedged in place asthe stone was moving through its alluvial environment.This discovery suggests that the Dry Cottonwood Creekarea might also have potential for gold recovery.

Highly translucent green serpentine from Afghanistan.Franck Notari of GemTechLab in Geneva, Switzerland,provided contributing editor Emmanuel Fritsch and thegemology laboratory at the University of Nantes withseveral highly translucent yellowish green beads (figure13). These poorly polished beads came from necklacesthat were reportedly purchased in Afghanistan. One beadwas sawn in two and polished for gemological testing.Refractive index measurements varied between 1.563and 1.567, and the specific gravity (determined hydrostat-ically) was 2.55 ± 0.05. These data are typical for serpen-tine. Further testing was required to identify the particu-lar species in the serpentine “subgroup” of the kaolinite-serpentine mineral group. Energy-dispersive spec-troscopy, with the University of Nantes SEM-EDX sys-tem, showed the presence of oxygen, magnesium, andsilicon, with lesser amounts of aluminum and iron.(Although oxygen can be detected with this system,hydrogen cannot.) The X-ray diffraction pattern was anexcellent match for a monoclinic polytype of antigorite,antigorite-6M, which is a serpentine mineral. Thechemical formula usually quoted for antigorite is

(Mg,Fe2+)3Si2O5(OH)4; the yellowish green color isprobably caused by the iron present.

Etch-decorated topaz. Two interesting samples of color-less topaz were recently sent to the Gem News editorsfor photodocumentation and gemological investigationof their inclusions (figure 14). Bill Larson, of PalaInternational, Fallbrook, California, reported that bothsamples were from the Mogok region of Myanmar.

The cabochon was thought to contain inclusions ofthe mineral goethite (an iron oxyhydroxide), as suggestedby the brown color and acicular habit. When these inclu-sions were viewed with magnification, however, their

Figure 12. A cluster of gold micronuggets is visible ina surface depression on this sapphire from DryCottonwood Creek. Photomicrograph by John I.Koivula; magnified 15¥. The inset shows a small par-ticle of gold that appears to have been smeared intothe surface of the sapphire. Photomicrograph by JohnI. Koivula; magnified 40¥.

Figure 13. These unusually translucent yellowishgreen beads, reportedly from Afghanistan, are antig-orite, a serpentine mineral. Photo by A. Cossard.


appearance was identical to the so-called “rutilated”topaz that was described and documented in theSummer 1987 issue of Gems & Gemology (J. Koivula,“The rutilated topaz misnomer,” pp. 100–103). Althoughthe inclusions in the topaz crystal were identical inshape to those in the cabochon, they were colorless. Allthe inclusions in both samples appeared to reach the sur-face of their host topaz.

In the earlier Gems & Gemology article, Brazilian“rutilated topaz” was actually shown to contain ribbon-shaped (to somewhat more prismatic) etch channels thatwere stained by limonite. The channels probably formedas surface-reaching fissures during growth of the topazand were significantly enlarged through later etching bycorrosive hydrothermal fluids. The “earthy” yellowishbrown limonite was later deposited in the channels byiron-rich groundwaters. Therefore, although the inclu-sion channels co-existed with the growth of the topaz,the filled inclusions developed after the crystal hadformed; these were not solid mineral inclusions thatgrew at the same time as the topaz. (The channels wouldbe colorless if they were not stained or filled with epige-netic material.) The colorless channels present near thetermination of the topaz crystal in figure 14 indicate thatthis particular crystal may not have been exposed to thesame epigenetic solutions that entered the stone fromwhich the cabochon was cut; or perhaps the iron-richstains were removed during cleaning of the specimen.

Red, pink, and bicolored tourmaline from Nigeria.Tourmaline from Nigeria has been known in the gemtrade since at least the middle 1980s (see, e.g., GemNews: Spring 1988, p. 59; Spring 1989, p. 47; Spring 1992,p. 62). These stones originated from tin-bearing peg-matites in Kaduna State, as well as from a pegmatite beltsoutheast of Kaffi in central Nigeria (J. Kanis and R. R.Harding, “Gemstone prospects in central Nigeria,”Journal of Gemmology, Vol. 22, No. 4, 1990, pp.195–202). Gem-quality green, red, pink, and bicoloredtourmalines have been recovered. Recently, contributingeditor Karl Schmetzer provided information on a newtourmaline find in Nigeria.

In summer 1998, Nigerian traders at Idar-Obersteinoffered large parcels of gem tourmaline from a localitywest of the town of Ogbomosho, near the border withthe country of Benin. More than 100 rough crystals and10 faceted stones were loaned to Dr. Schmetzer by Karl

Figure 14. The 26.31 ¥ 20.08 ¥ 13.24 mm (62.68 ct)cabochon of colorless topaz contains etch channelsfilled with yellowish brown limonite. The crystal (73mm long) also contains numerous etch channels, butthese do not show any evidence of staining. Courtesyof Bill Larson; photo by Maha DeMaggio.

Figure 15. These tourmaline crystals come from anew find in Nigeria. Red, pink, colorless, and greenzones are typical, but grayish blue zones were alsoseen. The largest crystal, on the left, measures 49 mmlong and 13.5 mm across. Courtesy of Karl Egon WildCo.; photo by M. Glas.


Egon Wild Co. (Kirschweiler) and Julius Petsch Jr. Co.(Idar-Oberstein). Dr. Schmetzer described the crystals asprismatic in habit (figure 15), with trigonal prism faces m{011–0} and hexagonal prism faces a {112–0}; the dominanttrigonal pyramid faces were o {022–1}, sometimes in com-bination with ditrigonal pyramid x {123–2} faces. The rela-tive size of the terminal face, or pedion, c (0001) variedfrom small to large (figure 16).

Most of the crystals were color zoned purplish red topink to nearly colorless. In some samples, the growthzones adjacent to the pedion (parallel to the pyramidfaces) were medium to intense yellowish green or green;rarely, this end of a crystal was bluish gray (again, see fig-ure 15). The pleochroism for the red and pink zones wascolorless to medium pink parallel to the c-axis, andintense pink to red perpendicular to the c-axis. For greenzones, it was light yellowish green parallel to the c-axis,and intense yellowish green or green perpendicular tothis axis. For the bluish gray zones, pleochroism waslight grayish blue parallel to the c-axis, and intense gray-ish blue perpendicular to this axis.

The faceted stones were evenly colored red or pink(figure 17), bicolored green and pink (and, rarely, blue andpink), or color zoned in various shades of red and pink.The refractive indices and specific gravities varied withinrelatively small ranges: nw = 1.640 and ne = 1.620 (both ±0.002); specific gravity = 3.05 ± 0.02. On the basis of visi-ble absorption spectroscopy, Dr. Schmetzer determinedthat Mn3+ was the dominant chromophore in the red andpink samples.

TREATMENTS

On the burning of polymer-impregnated synthetic andnatural opals. In polymer-impregnated gem materials(e.g., opal, turquoise, and jade), the question sometimesarises as to how much polymer is present. This is espe-cially a cause for concern with opal, since the refractiveindex and specific gravity values of the polymer com-pound(s) commonly used are so similar to those of theopal itself. Furthermore, the two materials are not easilydistinguished by visual examination, even with themicroscope. Consequently, the amount of polymer pre-sent is generally unknown, and might constitute a signif-icant portion of the weight of a sample.

In addition, the Materials Safety Data Sheets providedwith polymers state that many are flammable. To studythis possible durability concern, as well as to investigatethe amount of polymer present in some natural and syn-thetic opals, Gem News editor Mary Johnson and GIAGem Trade Laboratory staff gemologist Maha DeMaggiodestructively tested seven samples by burning them.Since heat drives off both water and volatile organicmaterials (such as some of the breakdown products ofheated polymers), the approximate amount of these sub-stances present can be measured by weighing the samplebefore and after heating. Although this test would not be

applied in the course of routine gem testing, it does pro-vide some idea of the potential weight component of thepolymer in such treated synthetic opal (which, based onearlier research, appears to be largely anhydrous).

The samples used were: one (untreated) “white”Gilson synthetic opal (2.43 ct), one (untreated) “blackcrystal” Gilson synthetic opal (1.13 ct) [Gilson syntheticopals are not polymer-treated, in our experience], fourpolymer-impregnated synthetic opals (0.21, 0.65, 1.39,and 8.14 ct), and one polymer-impregnated natural opal

Figure 16. These schematic drawings illustrate thecrystal faces seen on the tourmaline crystals recentlyfound in Nigeria. Variations in the size of the pedionc (0001) face primarily account for the differences inmorphology between the two crystals. After drawingsby Karl Schmetzer.

Figure 17. Attractive faceted stones are being cutfrom the new find of Nigerian tourmaline, such asthis 21.10 ct rectangular cushion. Courtesy of BillLarson; photo by Maha DeMaggio.


from Brazil (1.14 ct). We attempted to ignite each sampleusing a match or an alcohol burner; this was done in afume hood, to avoid exposure to (possibly toxic) combus-tion gases.

All the polymer-impregnated samples caught firereadily (figure 18), and they continued to burn whenremoved from the flame. The four polymer-impregnatedsynthetic opals lost 16%–27% of their weight by burn-ing, with an average weight loss of 21%. Because theresulting residue broke apart easily, we did not attempt

to burn the samples all the way through, so these valuesrepresent the minimum weight of the polymer in thesesamples. Subsequent microscopic examination showeddeep cracks throughout, as well as charred droplets ofexsolved polymer (figure 19). The impregnated naturalopal also burned, although somewhat less readily.Because this stone broke apart during examination,weight loss from the burning alone could not be deter-mined. The two Gilson synthetic opals (which had notbeen polymer-impregnated) reacted the least: The “blackcrystal” synthetic opal appeared unchanged, while the“white” opal became more transparent. Neither lostweight or caught fire.

In a previous examination of polymer-impregnatedsynthetic opals (“Kyocera plastic-impregnated syntheticopals,” Summer 1995 Gem News, pp. 137–139), wereported the results of heating experiments performed byJeffery Bergman in Bangkok, who found weight losses ofabout 20% at 600°C. The results of the simple pyrolysistest reported here are consistent with this finding.

In the 1995 study, scanning electron microscopyrevealed that Kyocera polymer-impregnated syntheticopal contains organized aggregates of small silica spheres,as does natural opal. The polymer may stabilize the silicalattice and improve both the durability (under normalwear conditions) and clarity of the synthetic opal.However, the flammability hazard that is now intro-duced may be a consideration for the wearer of such apiece, as well as for the jeweler (although we would notexpect a jeweler to use direct flame in the vicinity of anopal).

Irradiated inclusions in topaz. At the 17th IMA meetingin Toronto, Ontario (reported above), I. L. Komov (StateScience Centre of Environmental Radiogeochemistry,Kiev, Ukraine) reported that colorless halite (NaCl),sylvite (KCl), and villiaumite (NaF) crystals in fluidinclusions became yellow, “lilac-colored,” and brown,respectively, when exposed to gamma radiation (the hostmineral was not specified). Over a decade ago, in 1987,the late Charles Ashbaugh, then at UCLA and collabo-rating with GIA in Santa Monica, examined one suchexample. The core of a colorless sylvite in a fluid inclu-sion in a Nigerian topaz became purple after exposure toionizing radiation from a linear accelerator (“linac” treat-ment; figure 20). (The sylvite identification was con-firmed by Chuck Fryer of GIA GTL, using X-ray powderdiffraction analysis.) The topaz itself turned blue. At thetime, Mr. Ashbaugh and John Koivula speculated thatthe presence of such purple crystal inclusions mightprove that a topaz had been irradiated, as sylvite crystalsin natural-color near-colorless and brown topaz are near-colorless. Unfortunately, this project was never pursued.However, Dr. Komov’s IMA presentation supports theseearlier findings. For more on irradiated gems, see C. E.Ashbaugh III, “Gemstone irradiation and radioactivity,”Gems & Gemology, Winter 1988, pp. 196–213.

Figure 19. After burning, droplets of charred polymerresidue can be seen on the surface of this impregnat-ed synthetic opal; a network of cracks is also visible.Photomicrograph by John I. Koivula; magnified 20¥ .

Figure 18. This 8.14 ct polymer-impregnated synthet-ic opal burned readily in the flame of an alcoholburner. Photo by Maha DeMaggio.


SYNTHETICS AND SIMULANTS

Obsidian imitation. On a visit to Idar-Oberstein,Germany, one of the editors (JIK) found an attractiveglass sphere in one of the many gem and jewelry shopsthat make this area famous. Represented as “obsidianfrom Russia,” this well-polished sphere was relativelylarge (approximately 9 cm in diameter) and opaque. Thesphere was predominantly a mottled brownish green,with a diffused stripe of lighter green to grayish greenthrough the center. Perhaps the most distinctive feature,however, was the presence of numerous spherical inclu-sions with a silvery metallic luster that appeared as cir-cles scattered over the entire surface. These inclusionsranged from well under a millimeter to just over 3 mm indiameter. If in fact this object was a natural glass, then itwas certainly unusual. The sphere’s cost however, madeits acquisition for scientific examination impractical.

This “problem” was solved shortly thereafter withthe discovery by this editor of a partially polished pieceof the distinctive glass in a box of cutting scraps and crys-tal fragments at the shop. This piece weighed about 213grams and measured 8.3 cm on its largest dimension (fig-ure 21). It had one large, flat, polished surface, while theopposite side was “rough.” The botryoidal appearance,flow structure, and bubble pits on the unpolished sur-faces made it obvious that this was not obsidian or anyother form of natural glass. It was apparent that this largemass, and the sphere that had been fashioned from thesame material, were a form of slag (manufactured) glass.

The refractive index of this glass was 1.606. It showedno fluorescence to UV radiation. No absorption spectrumwas visible with incident illumination. The specific grav-ity was determined hydrostatically to be 2.99, although itwas undoubtedly influenced by the numerous metallic-appearing inclusions present.

Chemical analysis showed that this glass containedseveral elements in addition to the expected silicon.EDXRF chemical analysis (by Sam Muhlmeister of GIA

Research) showed the presence of barium, calcium, cop-per, iron, manganese, potassium, rubidium, strontium,and titanium. A few small fragments were broken off thesample so that the spherical metallic inclusions could beextracted, cleaned, and analyzed separately by EDXRF.These proved to contain primarily manganese, possiblyas an oxide.

Diffusion-treated synthetic sapphire. Contributing editorKarl Schmetzer has sent word that greater quantities ofdiffusion-treated synthetic sapphires are showing up onthe market in Bangkok, Thailand. Diffusion-treated nat-ural sapphires have been known in the trade since thelate 1970s (see, e.g., R. E. Kane et al., “The identificationof blue diffusion-treated sapphires,” Gems & Gemology,Summer 1990, pp. 115–133), but large quantities againbecame available in recent months. One diffusion-treat-ed synthetic blue sapphire was mentioned as early as1982 (Summer 1982 “Lab Notes,” p. 107), but the treaterof that sample might not have known that it was syn-thetic. The first notice that larger parcels of syntheticsapphires were being treated in this fashion was issued in1992 (R. C. Kammerling et al., ICA Laboratory Alert No.55, June 2, 1992). Recently, similar large parcels wereoffered in the Bangkok market, and the appearance ofthis material at other trading sites is only a matter oftime.

Five faceted samples, submitted by gem dealer M.Steinbach, were made available to Dr. Schmetzer forexamination. They were comparable in color to good-quality natural sapphire of Sri Lankan origin. Absorptionspectroscopy showed that the color of the samples wasdue to Fe2+/Ti4+ charge transfer, which is also commonfor natural blue sapphire.

No inclusions or growth patterns that are typical ofnatural stones were observed in any of these samples

Figure 20. In this linear-accelerator-treated piece ofblue topaz, a fluid inclusion contains several phases.The core of the colorless sylvite crystal turned pur-ple from the irradiation. Photomicrograph by J. I.Koivula; magnified 80¥ .

Figure 21. Represented as obsidian from Russia, thisdecorative glass proved to be manufactured. Photo byMaha DeMaggio.


when viewed with the microscope. Two of the samplesrevealed a number of tiny gas bubbles, indicating that theywere Verneuil-grown synthetic sapphires. However, Dr.Schmetzer did not observe any of the curved color bandingthat is also typical of Verneuil-grown synthetics, andwould have been expected if the color were inherent in thematerial (instead of being due to diffusion treatment).

As described in the references cited above, the diffu-sion treatment of either natural or synthetic sapphirescan be identified (often macroscopically) when the sam-ple is immersed in methylene iodide (or observed usingdiffuse transmitted white light). This was the case for thepresent samples, all of which showed an uneven col-oration from one facet to the next (figure 22). This pat-tern is caused by variation in the thickness of the diffu-sion layer on different facets that results from the repol-ishing that is always necessary after diffusion treatment.In most of the samples, a greater color concentration wasalso observed along facet junctions (also visible in figure22). Four of the samples had cavities on the surface thatwere filled with a dark-blue-appearing solid material (fig-ures 22 and 23). In two of these samples, some of the cav-ities were only partially filled. With SEM-EDX analysis,Dr. Schmetzer found that the material in each cavity wasactually a tiny synthetic sapphire crystal.

ANNOUNCEMENTS

Indonesian South Sea Pearl auction. Philmore USA andPT Philmoremas have organized a group of IndonesianSouth Seas pearl producers, whose harvests will be soldat ISSPA 1999. This is the first such auction to be held,and will occur on February 8–9, 1999, at the Hong KongConvention and Exhibition Centre. For further informa-tion, contact Philmore USA representative Stephen

Church at 836 Woodshire Lane K-6, Naples, Florida34105; phone 941-263-9371; FAX 941-263-9371; [email protected].

Congratulations to Gems & Gemology authors KurtNassau, James E. Shigley, and Shane McClure. TheirWinter 1997 article “Synthetic moissanite: A new dia-mond substitute” won a Certificate of Achievementfrom the American Society of Association Executives1998 Gold Circle competition. This is the 10th awardthat Gems & Gemology has won in this competitionsince 1992.

Note. The entry “‘Wild Life’ assembled natural gemstonecabochons” in the Fall 1998 Gem News section was con-tributed by Emmanuel Fritsch.

ERRATA:1. The photograph of Dr. George Rossman and Richard

T. Liddicoat in the Fall 1998 Gem News (p. 230, fig-ure 23) was taken by Judy Colbert.

2. In the Fall 1998 Gem News entry “Color-changepyrope-spessartine garnet, also from Madagascar”(pp. 222–223), the positions of the UV-visible absorp-tion bands were listed incorrectly. The correct wave-lengths for the Mn2+ bands are 408, 413, 422, and 483nm, and the Fe2+ bands are at 459 and 503 nm.

3. On p. 164 of the Hemphill et al. article “Modeling theAppearance of the Round Brilliant Cut Diamond: AnAnalysis of Brilliance” (Fall 1998), the source for theinformation given in table 3 on the EuropeanGemological Laboratory (EGL) should have been listedas Federman, 1997.

Figure 22. The uneven color distribution betweenfacets and the color concentrations along facet junc-tions—both typical of diffusion-treated sapphire—are best seen with the samples immersed in methy-lene iodide. The dark spots on four of the samplesare cavities that were found to be filled with syn-thetic sapphire. Photo by M. Glas.

Figure 23. A dark-blue-appearing synthetic sapphirecrystal is seen within a cavity on the surface of thisdiffusion-treated synthetic sapphire. Photomicrographby Karl Schmetzer; magnified 50¥ .

Book Reviews GEMS & GEMOLOGY Winter 1998 303

BULGARI By Daniela Mascetti and AmandaTriossi, 225 pp., illus., publ. byAbbeville Press, New York, NY,1996. US$75.00*

Bulgari is a welcome addition to thegrowing body of jewelry history liter-ature. Not only are the luscious pho-tos of sumptuous jewels a feast forthe eyes, but the book is also a lucidand thorough portrayal of this promi-nent jewelry company.

Each of the 12 chapters focuseson a specific aspect in the develop-ment of Bulgari’s distinctive style.Chapter one traces the history of theBulgari firm from its modest begin-nings in a small Greek village nearthe Albanian border to internationalsuccess by following the life ofSotirios Bulgari, the founder of thefirm. Sotirios, the only survivingchild of a Greek silversmith, wasborn in 1857. His steady progressfrom silversmith to fine jeweler wasthe base on which the Bulgari firmwas built. This chapter also showshow each successive generation con-tributed to the growth of Bulgari anddescribes some of their importantclients and significant jewelry sales.

The next chapter, The Evolutionof the Bulgari Style, demonstratesBulgari’s transition from followingjewelry fashion (between 1920 and1950) to leading it (from the 1960s tothe present). We are shown howBulgari designers introduced smooth,rounded elements that gave a senseof volume to their jewelry and incor-porated colored gemstones for chro-matic effect. Bulgari also chose to usemore yellow gold for importantpieces, in response to their cus-tomers’ desire for jewelry that couldbe worn at any time of day and forany occasion.

The authors go on to addressthree important design innovations

introduced by Bulgari that are nowpart of their signature style: the inte-gration of ancient coins in jewelry,the use of modules, and the use of aflexible band called a tubogas.During the 1960s, Bulgari revived thestyle of setting ancient coins in jew-elry, which had been out of fashionsince the end of the 19th century.The company also introduced theconcept of using modules—simple,interlocking elements made of pre-cious metals and/or carved gemsassembled in different combinationsto make necklaces, earrings, brace-lets, and rings. The tubogas, namedfor its resemblance to a gas-pipe, is aflexible band of interlocking thinstrips made without solder, used byBulgari for collar necklaces, bracelets,watch bands, and rings.

Manufacturing aspects includediscussion of the sense of volume thatis built into each piece with metal-work and gems, the selection and cutof gemstones used by Bulgari, and theproduction of their jewelry, fromdesign concept to finished product.These chapters are particularly inter-esting for the jeweler/gemologist.Each of Bulgari’s line of luxury itemshas its own chapter: Silver andPrecious Objects, Watches, andPerfumes. The book closes with achapter titled the Bulgari Image,which is an enlightening examinationof how Bulgari has carefully craftedthe image they present to the publicthrough advertising and store design.

The authors and the art directordeserve special merit for the visualimpact of this book. The jewelry islaid out and photographed so thereader can truly appreciate its mag-nificence, and many important jew-els are shown from front and back toillustrate the beautiful gallery workand clasps. Also, close-up details pro-vide an immediate understanding ofBulgari’s manufacturing excellence.

The exceptional illustrations and thein-depth text make this book a use-ful reference for jewelry historians,collectors, and appraisers. Yet it isalso an enjoyable read for anyoneinterested in a taste of luxury.

ELISE B. MISIOROWSKIJewelry Historian

Los Angeles, California

COLLECTING ANDCLASSIFYING COLOREDDIAMONDS: An IllustratedStudy of the Aurora CollectionBy Stephen C. Hofer, 742 pp., illus.,publ. by Ashland Press, New York,NY, 1998. US$300.00*

This heavy, lavishly illustrated bookdelivers more than 700 pages on thevarious aspects of colored diamondcollecting, with an emphasis on theobservation, determination, and clas-sification of a stone’s color. The bookis based on the 260 stones of theAurora collection, which has beendisplayed at the American Museumof Natural History in New York.

A brief introduction precedes acatalog of the entire Aurora collec-tion. Each gem is illustrated, and itsweight, dimensions, shape, cuttingstyle, and color description indicated.Following the catalog is a concise dis-cussion of important considerationsin colored diamond collecting. Rarityis addressed at some length, as it ispivotal to the estimation of value.This naturally leads to a discussion ofvalue, which is illustrated by a tableof auction prices according to dia-mond color. Then the major sectiondevoted to color begins, with com-ments first on color observation and

Susan B. Johnson & Jana E. Miyahira, Editors

*This book is available for purchase throughthe GIA Bookstore, 5345 Armada Drive,Carlsbad, CA 92008. Telephone: (800) 421-7250, ext. 4200; outside the U.S. (760)603-4200. Fax: (760) 603-4266.

Book Reviews

304 Book Reviews GEMS & GEMOLOGY Winter 1998

grading, then on how to determineface-up color (see below). The longestof the 12 chapters (at nearly 200pages, a book in itself) is devoted tocolor classification. It is organized bycolor (white, gray, black, purple, pink,red, orange, brown, yellow, “olive,”green, blue, and colorless) and empha-sizes the various nuances. Threeappendices complete the book: (1)cut and color determination graphs;(2) a glossary and an extensive bibli-ography; and (3) a list of diamondssold at auction, classified by color.

This is clearly not a book on col-ored diamonds in general, as it isstrongly biased toward collecting andclassifying. One feels that the bookwas written for the pleasure of shar-ing knowledge, rather than as ascholastic or scientific treatise. Assuch, it fulfills its purpose remark-ably well. The collector will find allsorts of interesting information, aswell as attractive color photographsthat can also be used for reference.

The book’s size (approximately 32¥ 24 ¥ 6 cm, or 12½ ¥ 9½ ¥ 2½ inches)and cost may be intimidating tosome, but the overall quality of theproduction is excellent. The 700-pluscolor photos, a number of them byworld-renowned photographer TinoHammid, are of high quality, as arethe numerous line drawings andcolor sketches. One of the great mer-its of this book is that the photos ofgroups of colored diamonds include acolorless diamond for visual refer-ence. One wishes this could havebeen done for the catalog section;although pictures of colorless dia-monds are available for comparison,these photos were not necessarilytaken under the same conditions asthose of the colored diamonds.

The text is easy to read, evenwhen it comes to the more delicateaspects of color science (such materi-al was enhanced by contributionsfrom Nick Hale, a professional colorscientist). Mr. Hofer should be com-mended for his remarkable bibliogra-phy, which provides an excellentbase for further research. References

to other authors are numerous andoffer a welcome support to the text.

The value of the text is limited,however, by the fact that Mr. Hofermakes no particular effort to com-pare his views with those of majorplayers in the field. For example, theuse of the catalog as a reference forcollectors is significantly limited bythe fact that it does not provide GIAcolor grades (although, as most auc-tion houses and colored diamonddealers agree, this is the most widelyaccepted color grading system in theindustry today). The author offers hisown system to estimate color, withnew concepts such as the CAMP(“colour-area micro pattern”) and theweighted average face-up color, butthe relationship between theseparameters and the color terms usedto describe the diamonds is not clear.Mr. Hofer also insists on giving eachof the Aurora collection stones acommon name, but such qualifiersas jade, heliotrope, “manilla,” andlead are uncommon for colored dia-monds, to say the least.

This beautiful, well-documentedbook is certainly a must-have for gembook and colored diamond collectors.Its superb documentation base willbe an asset for scholars as well.However, in addition to the idiosyn-cracies in the discussion of color, thefact that there is little on practicalconcerns such as the separation ofnatural from treated or synthetic col-ored diamonds in this work makes itless useful for the gemologist outsidethe collector community.

EMMANUEL FRITSCHInstitut des Matériaux de Nantes

Nantes, France

THE NATURE OF DIAMONDSEdited by George E. Harlow, 278pp., illus., publ. by CambridgeUniversity Press, New York, NY,1998. US$29.95* (softbound)

The Nature of Diamonds is the com-panion text for a special AmericanMuseum of Natural History exhibi-

tion of the same name. Its statedfocus is to provide a well-illustratedoverview of the diverse topics relatedto diamond. It is successful in thisendeavor—both in content and inillustration.

In The Nature of Diamonds, lead-ing scientists, gemologists, and cul-tural observers cover virtually everyaspect of this cherished gem. Thereader experiences a panoramic view,ranging from how diamonds form totheir economic, social, and techno-logical incarnations. Whether yourinterest in diamonds leans towardthe romantic, the symbolic, or thescientific, you will enjoy the diversi-ty of subject matter and the expanseof photos and illustrations.

Individual essays address threebroad categories: science, history, andutility. Beginning with the science ofdiamonds, chapters examine dia-mond’s unique mineralogy, the caus-es of color (both natural and artifi-cial), the extreme environmentsrequired for formation, and a globaltimeline of sources and production.Subsequent chapters explore the roleof diamonds throughout history,their diverse mythology and literarypresence, and their evolving culturalstatus. Remaining chapters highlightdiamond mining and processing, pro-vide a brief excursion into the gemol-ogist’s world of identifying and grad-ing gem diamonds, and give insightsinto the role of diamonds in moderntechnology.

Additional sections encompass apictorial guide to the world’s greatestdiamonds and the diamond treasuresof Russia. Two monographs cover thehistory of diamond cuts and the fasci-nating story behind the evolution oftoday’s symbol of love and marriage,the diamond ring. Each chapterincludes an ample bibliography.

The book’s editor (and one of thesubject specialists) characterizes TheNature of Diamonds as an overviewof the expansive world of diamonds.However, it accomplishes far morethan his modest statement mightconvey. This compendium of essays

Book Reviews GEMS & GEMOLOGY Winter 1998 305

penned by renowned experts, punctu-ated with numerous illustrations andphotographs, and packaged withvaluable bibliographical references, isan important resource for any library.

Whether you cherish diamondsfor their status, their economic andsocial legacy, or their unique scientif-ic applications, you will be enter-tained and enriched by The Nature ofDiamonds.

SHARON WAKEFIELDNorthwest Gem Lab

Boise, Idaho

GLOSSARY OF GEOLOGY,4th EditionEdited by Julia A. Jackson, 769 pp.,publ. by the American GeologicalInstitute, Alexandria, VA, 1997.US$110.00

Over the past few decades, the scopeof gemology has expanded consider-ably, particularly in the areas of geol-ogy and analytical techniques. As aresult, today’s gemologist needs amore solid technical vocabulary thanever before. For geology and relatedfields (e.g., geophysics), the Glossaryof Geology has been the best avail-able dictionary of specialized termsin English since its first edition waspublished in 1957. The fourth editioncontinues this tradition of excellence.The Glossary now contains about37,000 entries, of which 3,400 are newand 9,000 have been updated, expand-ed, or revised since the publication ofthe third edition only 10 years ago.

The 4,000-plus mineral namesconstitute the largest single group ofentries in the Glossary. Therefore, itis not surprising to find such terms asbenitoite, californite, chrysoprase,demantoid, rhodolite, and tanzanite,although some gem variety namessuch as tsavorite are not included.Among the more traditional gemo-logical terms, diaphaneity, enhance-ment, melee, and Tolkowsky theoret-ical brilliant cut do appear, but man-ufactured materials such as cubic zir-conia, GGG, and YAG are groupedtogether under diamond simulant.

There are also entries for most of theanalytical techniques likely to beencountered by gemologists, such asinfrared absorption spectroscopy,Raman spectrometry, and X-ray fluo-rescence (XRF) spectroscopy; onlyED[energy dispersive]XRF was notpresent from among my arbitraryselection of terms.

Without hesitation, I recommendthis Glossary to all gemologists asthe most authoritative work of itstype in English. Given the history ofthe Glossary and the size of thisfourth edition, it is not likely thatanother edition will appear for atleast a decade, which makes this vol-ume a good long-term investment.

A. A. LEVINSONUniversity of Calgary

Calgary, Alberta, Canada

GEM AND JEWELLERYYEAR BOOK 1997–98Edited by V. V. Kala and A. Kala,697 pp., illus., publ. by InternationalJournal House, Jaipur, India[[email protected]], 1998.US$35.00 (surface), US$50.00 (air)

Thirty-five years ago, India was aninsignificant player in the diamondworld, constituting less than 5% ofany aspect of the industry. Today, itdominates in the manufacturing sec-tor by virtue of its production ofabout 40% by value and 70% byweight of the world’s polished dia-monds, and by being home to at least90% of the world’s diamond cuttersand 20% of De Beers’s sightholders.Further, India-based companies aregarnering strength in downstreamjewelry manufacturing and retailing.The gem and jewelry industry is nowa vital component of the nationaleconomy, having become India’ssecond-largest source of foreignexchange—at 18%, surpassed only bytextiles. How did this all occur? Howdo Indian diamantaires view theindustry? And, what is the prognosisfor India’s influence on the diamondindustry in the next millennium?

These are not easy questions to

answer, but some indications can begleaned by perusing Gem andJewellery Year Book 1997–98. Nowin its 19th year of continuous publi-cation—primarily for the gem andjewelry industry in India—thissourcebook is little known else-where. It is primarily concerned withthe diamond industry, a reflection ofthe fact that polished diamondsaccount for the bulk (93%) of India’sgem and jewelry exports.

The book is divided into threeparts. Part I (358 pp.) covers a vastamount of material from the miningto retailing of diamonds. Topicsinclude: a review of recent highlightsin the Indian diamond industry;industry statistics that are difficult toobtain elsewhere; descriptions, withphotographs, of new Indian-mademanufacturing tools and technology;a “Who’s Who,” with brief profilesand photographs, of 171 Indian gemand jewelry luminaries worldwide;and glimpses of 38 world diamondmining and consuming countriesfrom an Indian perspective. Part II(132 pp.) consists of nine appendices,ranging from a list of worldwidegem and jewelry organizations to alisting of India’s diplomatic andtrade representatives abroad. Part III(198 pp.) contains lists (with address-es and specialties) of over 3,500selected international exporters andimporters—from 55 countries—forgemstones, jewelry, pearls, and syn-thetic stones.

This volume clearly indicatesthat India has built up a formidablegem and jewelry infrastructure, par-ticularly with respect to diamonds. Itis also clear that the Indian diaman-taires have the knowledge, finances,and ability to expand their influence.Those in the international gemindustry who choose to ignore thisunique and valuable handbook, withits wealth of information and sub-liminal implications, do so at theirown risk.

A. A. LEVINSONUniversity of Calgary

Calgary, Alberta, Canada

306 Gemological Abstracts GEMS & GEMOLOGY Winter 1998

COLORED STONESAND ORGANIC MATERIALSThe color of money. M. Lurie, Colored Stone, Vol. 11, No.

3, 1998, pp. 42–44, 46, 48, 50.Besides being a source of national pride and Colombia’sfifth-largest export commodity, emerald represents alivelihood for an estimated 300,000 people in Colombia.With the pending creation of an emerald bourse, the gov-ernment is hoping that increased demand (which hasbeen down in recent years) will push Colombian emeraldexports into the same class as the country’s coffee and oilexports.

In light of these high expectations, the article discuss-es the production capabilities of Colombia’s top threeemerald mines: Muzo, Cosquez, and Chivor. Muzo andCosquez have historically been the richest mines, withCosquez producing more than Muzo in recent years.Chivor’s potential, though, is still largely untapped, and ithas turned out some exceptionally high-quality material.Chivor specifically has benefited from modernized meth-ods and foreign investment. Stuart Overlin

Opals: Gems of lore and luster. G. Butler, Rock & Gem,Vol. 27, No. 10, October 1997, pp. 16–18.

Intrigue has surrounded opal since ancient times. It wasonce thought to possess great medicinal value, particu-larly for the glands. It was also considered the bearer ofcertain magical qualities—ensuring fidelity, enhancingmemory, making the wearer invisible, and serving as an

ABSTRACTSGemological

EDITOR

A. A. LevinsonUniversity of Calgary,

Alberta, Canada

REVIEW BOARD

Peter R. BuerkiGIA Research, Carlsbad

Jo Ellen ColeGIA Museum Services, Carlsbad

Maha DeMaggioGIA Gem Trade Laboratory, Carlsbad

Professor R. A. HowieRoyal Holloway, University of London

Mary L. JohnsonGIA Gem Trade Laboratory, Carlsbad

Jeff LewisGIA Gem Trade Laboratory, Carlsbad

Margot McLarenRichard T. Liddicoat Library, Carlsbad

Elise B. MisiorowskiLos Angeles, California

Jana E. Miyahira-SmithGIA Education, Carlsbad

Carol M. StocktonAlexandria, Virginia

Rolf Tatje Duisburg University, Germany

Sharon WakefieldNorthwest Gem Lab, Boise, Idaho

June YorkGIA Gem Trade Laboratory, Carlsbad

This section is designed to provide as complete a record as prac-tical of the recent literature on gems and gemology. Articles areselected for abstracting solely at the discretion of the section edi-tor and his reviewers, and space limitations may require that weinclude only those articles that we feel will be of greatest interestto our readership.

Requests for reprints of articles abstracted must be addressed tothe author or publisher of the original material.

The reviewer of each article is identified by his or her initials at theend of each abstract. Guest reviewers are identified by their fullnames. Opinions expressed in an abstract belong to the abstrac-ter and in no way reflect the position of Gems & Gemology or GIA.

© 1998 Gemological Institute of America

Gemological Abstracts GEMS & GEMOLOGY Winter 1998 307

aid to psychic visions and out-of-body consciousness, toname a few.

Included in this article is a description of opal byRoman scholar Pliny the Elder, who ranked it second invalue to emerald. The article shifts to the modern agewith a discussion of opal’s occurrences and gemologicalproperties, and in closing it illustrates the ongoing, stillmystical appeal of opal’s “fire.” Stuart Overlin

Oxygen isotope systematics of emerald: Relevance for itsorigin and geological significance. G. Giuliani, C.France-Lanord, P. Coget, D. Schwarz, A. Cheilletz, Y.Branquet, D. Giard, A. Martin-Izard, P. Alexandrov,and D. H. Piat, Mineralium Deposita, Vol. 33,1998, pp. 513–519.

There are ambiguities in identifying the geologic and geo-graphic origins of cut emeralds by conventional gemolog-ical means such as color, transparency, or inclusions. Thisproblem led the authors to investigate the usefulness ofoxygen isotope (d18O) data from emeralds. Samples (nospecific number given) from 62 locations in 19 countrieswere studied. This is a destructive technique, for which5–10 mg of sample is needed for the isotope analysis.

Three groups of oxygen isotope data are delineated,each of which generally corresponds to specific geologicenvironments and, in some cases, to specific countries,districts, or even deposits. The first two groups have rel-atively low oxygen isotope values (d18O = +6.2 to +7.9‰,and d18O = +8.0 to +12.0‰), and the majority of thesedeposits formed in association with granitic pegmatites.Most of the isotope values in these two categories over-lap and cannot be used alone to identify unambiguouslyeither individual deposits or country of origin. However,a few individual deposits can be identified by using solidand fluid inclusion information in conjunction with theisotope data. The third group, with higher oxygen isotopevalues (d18O > +12.0‰), consists of emeralds associatedwith faults and shear zones (e.g., from Colombia andAfghanistan). The oxygen isotope values in this group canbe differentiated from one another, allowing identifica-tion of the specific geographic source (country, district, ormine) for such emeralds. Because geographic origin mayinfluence the value of some gem-quality emeralds, theoxygen isotope method merits further research as a pos-sible tool in identifying country of origin. JL

A reexamination of the turquoise group: the mineral [sic]aheylite, planerite (redefined), turquoise andcoeruleolactite. E. E. Foord and J. E. Taggart Jr.,Mineralogical Magazine, Vol. 62, No. 1, 1998, pp.93–111.

The term turquoise applies not only to a mineral speciesbut also to a group of minerals with similar chemistryand structure, of which turquoise is the best known. Thegroup includes six (mostly rare) species (planerite,turquoise, faustite, aheylite, chalcosiderite, and anunnamed Fe2+-Fe3+ analogue) that have the general for-

mula A0–1B6(PO4)4-x(PO3OH)x(OH)8 • 4H2O, where x = 0–2.This paper summarizes the elemental site occupancies ofthe six species, and gives crystallographic (e.g., unit cell)data for all members of the group and X-ray diffractiondata for some (planerite, turquoise, and aheylite).

The established species, many of which may be blueor green, are indicated in the following table:

A complete solid solution exists between planerite andturquoise, and solid solutions exist to varying degreesbetween chalcosiderite and turquoise, and betweenfaustite and turquoise; these substitutions affect thecolor.

Study of the turquoise group is hindered by the lack ofpure material and the extremely small crystal size, whichaccount for the difficulty in obtaining accurate opticaland other physical data. Nevertheless, data are given forplanerite (density of 2.68 g/cm3, hardness of 5 on theMohs scale, mean R.I. ~ 1.60) and aheylite (density of 2.84g/cm3, biaxial (+), mean R.I. ~ 1.63).

The samples studied by these authors are fromBolivia, Russia, and the U.S. (Pennsylvania, Virginia, andArkansas). The authors suggest that, mineralogically,light blue or blue-green “turquoise” from many world-wide localities may be planerite rather than the speciesturquoise. [Editor’s note: The authors did not study mate-rial from the classic Persian locality for which the speciesis named, nor from other gemologically important locali-ties in Arizona and New Mexico. To the best of ourknowledge, the International Mineralogical Associationhas not yet made any rulings on the basis of this study.]

RAH

Tanzanite takes off. R. B. Drucker, Jewelers’ Circular-Keystone, Vol. 169, No. 4, April 1998, pp. 76–80.

Since its discovery in 1969, tanzanite has risen in popu-larity to the point that some believe it is the fourth mostimportant colored gemstone after emerald, ruby, and sap-phire. In only 30 years, tanzanite has gone from being acollector’s specimen to a successfully marketed retailgemstone. It has overcome the stigma of being “too soft,”in part because the industry has learned how to set andcare for the material properly.

The price of tanzanite has fluctuated widely since itsdiscovery. Prices reached their peak in 1984, at $750 percarat (wholesale) for extra-fine goods. Then, supply over-took demand and prices declined, reaching a low in 1993of $200 per carat for the same quality of goods. Ironically,

Mineral name A-site cations B-site cations

Planerite vacant AlTurquoise Cu AlFaustite Zn AlAheylite Fe2+ AlChalcosiderite Cu Fe3+

Unnamed Fe2+ Fe3+

this great price decrease became the main contributor totanzanite’s current popularity and a 50% price rise in thepast five years. The lower cost attracted the attention ofboth mass marketers (e.g., TV retailers) and traditionaljewelers and, consequently, consumers.

At present there is no synthetic tanzanite on the mar-ket, and the various simulants available can be detectedwith routine gemological tools (such as a refractometer);visual detection alone is difficult and not recommended.Buying tips are briefly discussed, with saturation beingthe key to fine color. JY

Time travelers. R. Weldon, Professional Jeweler, Vol. 1,No. 6, July 1998, p. 50.

Amber [defined as tree resin that is both fossilized andover one million years old—otherwise it is copal] withprehistoric insects and other organic inclusions offers abeautiful window into the past, and it may provide cluesto our own civilization. The best-known sources are inthe Baltic region (including Russia) and the DominicanRepublic. The price of amber takes into considerationseveral factors: the rarity of the trapped organic matter(shown is a prized specimen that contains a scorpion); thevisibility, size, and location of the inclusions; the condi-tion of the amber (including the amount of crazing); thegeographic origin; and the color (deeper colors, such asred, are most desirable). MM

DIAMONDSChameleon diamonds. M. Van Bockstael, Antwerp

Facets, December 1997, pp. 46–47.A new awareness of chameleon-type diamonds followedthe sale at auction of an important 22 ct stone in 1996.Chameleon diamonds are characterized by a repeatablecolor change and strong phosphorescence. Unlike the colorchange in alexandrite, which is seen when the stone isviewed with different light sources (day [fluorescent] orincandescent light), the color change in chameleon dia-monds may be observed only when the stone: (1) is heated;(2) is exposed to light after an extended period of time (daysor weeks) in the dark (e.g., a safe); or (3) is exposed to strongultraviolet (UV) illumination (in this case, gentle heatingmay be required to return the diamond to its original color).

There are at least three different types of chameleondiamond. The first changes from greenish yellow “olive”to bright yellow. The second is seen in some Argyle pinkdiamonds that change briefly to brownish pink withstrong UV illumination. The third (observed in only onediamond) involves a change from faint pink to colorlessafter exposure to UV radiation.

While the color changes are rapid and/or brief, the typ-ical greenish yellow phosphorescence of chameleon dia-monds is relatively long, lasting up to several minutes. Thephosphorescent behavior, “chameleonism,” and the occur-rence of H3 color centers in these diamonds may all berelated. For the purposes of grading chameleon diamonds,

the reported color is the one that is most stable, that is, thecolor of the stone after it has had ample time to equili-brate to normal lighting (and temperature) conditions.

Kim Thorup

De Beers beats BHP to Russian diamonds. J. Helmer,Business Review Weekly, Vol. 20, No. 10, March29, 1998, p. 30.

De Beers has obtained the right to develop the Lomonosovdiamond field, one of the world’s richest undeveloped dia-mond deposits [consisting of five diamond-bearing kim-berlite pipes]. It is located near Arkhangelsk in northernRussia. Soglasiye De Beers Mining Investments, a joint-venture company, has acquired at least 40%—more than23 million shares—of Severalmaz, the Russian companythat holds the license to develop the field. The Australiancompany BHP apparently was the only other serious for-eign contender.

With an initial outlay of less than $8 million, DeBeers now has firm control over foreign investment inthe Russian Arkhangelsk diamond fields, and is planningto spend an additional $50 million on feasibility studiesand mine development. De Beers has overcome the polit-ical and bureaucratic obstacles, and is confident aboutsolving the technical problems of mining the marshy ter-rain that is close to ecologically sensitive fish-breedinggrounds. Lori Ames

Diamonds in California. E. B. Heylmun, InternationalCalifornia Mining Journal, Vol. 66, No. 11, July1997, pp. 18–20.

“A few hundred” diamonds have been officially recordedas found in California, and possibly thousands have beendiscarded in the course of alluvial gold mining. Most ofthe recorded diamonds are yellow, chipped, and flawed;about 20% have been gem quality. Rarely, they arebrown, green, blue, or “red.” It is easy to overlook dia-monds while panning for gold, and the ones that havebeen found owe their discovery primarily to fortuitousflashes of light. Many California alluvial diamonds arecoated with a paint-like substance that obscures theiridentity; however, they may retain the octahedral mor-phology characteristic of diamond.

Although no kimberlite has been identified inCalifornia, ultramafic rocks such as peridotite, eclogite,and serpentinite are present in the Klamath, Coast Range,and Sierra Nevada Mountains. These rocks may be thediamond hosts. Most of the diamonds have been found inplacers in the Mother Lode region of the Sierras, but thisrecovery may reflect the relative rates of prospecting insource areas. Within the Mother Lode, diamonds havebeen found at Cherokee Flat (more than 400 diamonds, to6 ct), Thompsons Flat, French Corral (where the largeststone, weighing 7.25 ct, was found), Foresthill, SmithsFlat, Fiddletown, and Volcano. Several small diamondshave been found associated with platinum in theKlamath Mountains, especially near the junction of the


Trinity and Klamath Rivers, in Tertiary channel depositsand weathering surfaces. Small-to-microscopic diamondshave been found in beach sands from the Oregon borderdown to Monterey. MLJ

Emplacement and reworking of Cretaceous, diamond-bearing, crater facies kimberlite of central Sas-katchewan, Canada. D. A. Leckie, B. A. Kjarsgaard,J. Block, D. McIntyre, D. McNeil, L. Stasiuk, and L.Heaman, Geological Society of America Bulletin,Vol. 109, No. 8, 1997, pp. 1000–1020.

Over 70 kimberlites have been identified in the very large(30 ¥ 45 km) Fort à la Corne kimberlite field in CentralSaskatchewan, interspersed with sedimentary rocks.Although the kimberlite phases contain diamonds (0–23ct/100 tonnes), no economic deposit has yet been identi-fied. These kimberlites are unusual because they do nothave the cone shape characteristic of kimberlites fromSouth Africa and most other localities; rather, they areshaped like sheets or saucers and lack diatreme or rootzones. Therefore, only crater facies kimberlites are pre-sent, with large diameters and shallow depths. Theabsence of competent barrier rocks (e.g., basalts) in thesedimentary layers near the surface enabled the kimber-lite magma to erupt easily without forming the typicalcone shape.

Drill cores were obtained from one of the kimberlites,the Smeaton (950 m in diameter; 130 m at its thickestarea, tapering to only 20 m at its edges), by the GeologicalSurvey of Canada for research purposes. The Survey’sstudies show that about 101 million years ago the kim-berlites exploded onto the Earth’s surface in at least twoperiods of volcanism. The rock materials erupted into theatmosphere and eventually formed air-fall deposits ofvarious types. These were subsequently intermixed withboth marine and terrestrial sediments during suchprocesses as erosion and shoreline changes. Micro-diamonds are found in some of the air-fall deposits,which can only be interpreted to mean that diamondswere literally “falling from the sky”! AAL

It’s a rough world. K. Nestlebaum, Rapaport DiamondReport, Vol. 21, No. 1, January 9, 1998, pp. 59, 61,65.

The success of a rough diamond buyer depends on thebuyer’s ability to recognize and sort different types ofrough, and to determine their value. This must be donequickly, using only a few pocket instruments or simpletools. This article describes the various factors a buyermust consider in evaluating rough diamonds, using themajor categories of form, shape, and color.

Twelve different forms are described (e.g., closedstones, near-gems, macles, cleavables). On the basis ofshape, goods are categorized as sawable, nonsawable, andfancies. Sawables, of which well-formed octahedra anddodecahedra that finish into rounds are the best exam-ples, are more valuable than nonsawables because of their

greater finished weight retention. Elongated or distortedcrystals will finish into fancies (e.g., emerald cuts) thatare generally less expensive than rounds. Three categoriesof color are recognized. “Colorless,” the top category, isequivalent to the gemological color grades D to F; “tinted”refers to the color grades G to I; and “colored” includes themore saturated yellows, browns, and other fancy-colorstones.

Another factor in determining the value of rough dia-monds is size. Specially designed sieves are used to sepa-rate the various sizes. Sieve sizes begin at about 50 stonesper carat and increase up to about three stones per carat.

Most of the rough offered for sale is presorted andpackaged as a Central Selling Organisation “sight.”During a sight offering, the rough buyers (sightholders)can examine goods under the best conditions. Anotheroutlet is the Antwerp rough market, a 60-year-old boursewhere diamonds from mines outside of De Beers’s controlare traded; it is open to all buyers. Rough buyers can alsopurchase goods in certain source countries, where theycommonly must make important decisions under less-than-ideal lighting conditions. No matter where rough ispurchased, its ultimate value cannot be determined untilit has been cut and polished. JY

Making the cut: The journey from rough to polished. K.Nestlebaum, Rapaport Diamond Report, Vol. 21,No. 5, February 6, 1998, pp. 51, 65.

This article follows rough diamonds to their polishedstate through the following stages: cleaving, sawing, brut-ing, cross-cutting (creating four facets above and fourfacets below the girdle), and, finally, brillianteering (plac-ing the remaining facets). The importance and value ofthe skilled diamond cutter is emphasized. It concludesthat even though automation has been in existence andimproving for certain aspects of the cutting process (e.g.,laser sawing) for the past three decades, finer stones con-tinue to be cut by traditional methods. Modern machin-ery cannot make the decisions and judgments necessaryfor each individual stone, especially the more valuableones. JY

Trans Hex—The miner to marketer. C. Gordon,Diamond International, No. 52, 1998, pp. 57, 58,61, 62.

Trans Hex currently produces about 200,000 carats ofdiamonds annually in South Africa, primarily from sever-al alluvial deposits along the Orange River and inNamaqualand. This represents 2% of South African dia-mond production. Much of Trans Hex’s production is ofvery high quality: Orange River goods can be worth $600per carat. Because the established deposits are rapidlybecoming depleted, Trans Hex is developing new alluvialdeposits, the most promising of which are marine con-cessions in the Atlantic Ocean. Through Canadian-reg-istered Trans Hex International, exploration for newdiamond deposits is under way in Brazil, Indonesia,


Namibia, Angola, and several West African countries.Trans Hex markets its own diamonds using a unique,

and very successful, sealed-tender system. It holds“sights” in which potential buyers can view parcels. Topbuyers are attracted because they can submit bids for theparticular types of rough diamonds that suit their needs.This is distinctly different from the CSO “box system,”in which sightholders have limited options in their selec-tion of rough diamonds. AAL

Unusual diamonds and unique inclusions from NewSouth Wales, Australia. H. O. A. Meyer, H. J.Milledge, F. L. Sutherland, and P. Kennewell.Russian Geology and Geophysics [Proceedings ofthe Sixth International Kimberlite Conference],Vol. 38, No. 2, 1997, pp. 305–331.

Alluvial diamonds in eastern Australia were minedintermittently from 1852 to 1922, primarily in theCopeton/Bingara area of New South Wales (400 km northof Sydney). These diamonds are enigmatic because theycannot be related to any conventional primary source,such as a kimberlite or lamproite. Although the manysophisticated studies (e.g., carbon and nitrogen isotopes)that have been made uncovered some unique characteris-tics of these diamonds, none succeeded in determiningtheir provenance. After reviewing pertinent data, thispaper continues the search by examining a selection of 65documented diamonds collected between 1989 and 1992.The studies include: mineral inclusions, carbon andnitrogen isotope data, external features, cathodolumines-cence (CL) characteristics, and estimation of nitrogencontent and aggregation by infrared spectroscopy.

Important results are: (1) There are two major popula-tions of New South Wales diamonds, one white (lownitrogen, complex CL zoning) and one yellow (high nitro-gen, no CL zoning); (2) morphologically, there are almostno octahedra, which suggests substantial resorptionand/or transportation over long distances; (3) previousconclusions with respect to the unusual isotopic charac-teristics and mineral inclusions of these diamonds areconfirmed, and an augite inclusion—characteristic of aneclogitic origin—was identified; and (4) the diamondsformed in the temperature range of 1,180°–1,240°C.Notwithstanding these comprehensive data, no newhypothesis for the origin of the eastern Australia dia-monds is presented. AAL

GEM LOCALITIESChrome diopside & chrome enstatite: Rare gemstones.

W. D. Hausel, International California MiningJournal, Vol. 67, No. 7, March 1998, pp. 23–24.

The bright green chromium-rich varieties of diopside andenstatite are rare gem materials that can be found inWyoming and nearby states, in association with kimber-lite indicator minerals (e.g., pyrope) as well as diamonds.Gem-quality chromian diopside up to 5 cm (2 in.) long

has been found in the State Line district (along theColorado-Wyoming border) and in the Green River Basinin southwestern Wyoming. Today the latter is a betterplace to find both chromian diopside and chromian ensta-tite because of easier access. These materials can berecovered from stream sediments with careful use of agold pan. The sizes and quality of individual faceted (orfacet-grade) pieces are not mentioned in this article.

MLJ

Micro-PIXE analysis of trace element concentrations ofnatural rubies from different locations inMyanmar. J. L. Sanchez, T. Osipowicz, S. M. Tang,T. S. Tay, and T. T. Win. Nuclear Instruments andMethods in Physics Research B, Vol. 130, 1997, pp.682–686.

The authors analyzed 130 untreated rough rubies fromnine metamorphic localities in Myanmar, includingMogok and Mong Hsu, using micro proton-induced X-rayemission (PIXE). The concentrations of chromium, tita-nium, vanadium, iron, copper, and gallium—the mostabundant trace elements—were determined for a 200 ¥200 mm area on each stone. In a unique approach, theauthors used the trace-element mapping capability of theinstrument to eliminate inhomogeneities, such as inclu-sions, from the analyses for the areas examined.

The measurements revealed that, with the exceptionof gallium, there were large variations in the trace-ele-ment chemistry of rubies from the different localities, aswell as for rubies from the same locality. Nevertheless,some consistent differences were also found. Using sta-tistical analysis, including tree clustering and factoranalysis, the authors determined that the origin of rubiesfrom six of the nine localities could, indeed, be deter-mined using this technique. Sam Muhlmeister

Neue Edelsteinvorkommen (New gem deposits). U. Hennand C. Milisenda, Uhren Juwelen Schmuck,January 1998, pp. 51–53 [in German].

Tanzania emerged as a great producer of colored gem-stones in the second half of this century. Most of theimportant localities (e.g., Longido, Lake Manyara,Merelani, and Umba) are in the northern part of the coun-try; they produce a great variety of gems, the most impor-tant being tanzanite, corundum (ruby and fancy-colorsapphires), garnet (particularly rhodolite and tsavorite),tourmaline, emerald, alexandrite, spinel, and quartz.Diamonds are mined from the Mwadui kimberlite pipe,also in the north. Historically, gemstone occurrences inthe south have been rare.

In 1994, however, large and rich gem deposits werefound in southern Tanzania in the vicinity of Tunduru,about 80 km north of the border with Mozambique. Anestimated 80,000 “illegals” have been working the allu-vial deposits in the vicinity of the Muhuwesi and MtetesiRivers, mostly by primitive methods. Although the pri-mary sources of the gem minerals have not been found,


the fact that some crystals are only slightly rounded indi-cates short transport distances. This article discusses thehistory of the discovery and the development of gem-stone trade in this area, the geologic setting of thedeposits (in the Proterozoic Ubendian-Usagaran Systemof metamorphic rocks), and the most important gemmaterials found to date. These include blue and fancy-color sapphires, ruby, many colors of spinel, garnet(rhodolite, hessonite, and color-change), and chrysoberyl(cat’s-eye and alexandrite). PB

New gemstone occurrences discovered in Wyoming.International California Mining Journal, Vol. 67,No. 6, February 1998, pp. 7–8.

“Gem-quality” cordierite [iolite] and peridot have beendiscovered in Wyoming by the state Geological Survey.The cordierite is transparent and violet-blue; it is found asmineral grains up to 5 cm (2 in.) long in rock in the cen-tral Laramie Mountains, near Wheatland. The peridotoccurs in rock (to 2.5 cm across) or as smaller loosepieces; it is transparent and “olive-green.” The Surveyrecovered about 13,000 carats of peridot from alluvialsources in the Leucite Hills, near Rock Springs. Also, twoadditional kimberlite pipes have been located in theGreen River Basin, but no diamonds have yet been foundin either. MLJ

Pearls and pearl oysters in the Gulf of California, Mexico.D. McLaurin, E. Arizmendi, S. Farell, and M. Nava,Australian Gemmologist, Vol. 19, No. 12, 1997, pp.497–501.

For more than four centuries, Mexico’s Gulf of Californiawas a major source of colored pearls, but overfishing andpollution have greatly reduced production since the latterpart of the 1800s. This situation is now being reversedwith research into pearl culturing and the establishmentof pearl farms. This article describes the cultivation pro-cedures of the I.T.E.S.M. Perlas de Guaymas pearl farm inBacochibampo Bay, near Guaymas, which started opera-tions in 1996. The farm uses a suspended culture systemand new, Mexican-developed grafting technology. In1997, the farm produced 30,000 mabé pearls, and projec-tions for 1998 were to double this quantity. [Editor’s note:For further information on Baja California pearls, see M.Cariño and M. Monteforte, “History of pearling in La PazBay, South Baja California,” Gems & Gemology, Summer1995, pp. 88–105.] Scott Rebhun

A study of Korean precious serpentine. W.-S. Kim and S.-H. Cho, Journal of Gemmology, Vol. 26, No. 3,1998, pp. 156–164.

A new deposit of gem-quality serpentine was discoveredin 1995 in Booyo County, South Korea. The deposit formsalong both contacts of a garnet vein that cross-cuts a bodyof serpentinite (a rock consisting almost entirely of ser-pentine-group minerals). The gem-quality serpentine issemi-translucent, with a uniform deep green color; it has

a hardness of about 5, a resinous and waxy luster, a spe-cific gravity of 2.57–2.58, and a refractive index of about1.56. The color changes from deep green to orange-pinkwhen the material is heated at 850°C.

X-ray powder diffraction analysis identified the gemserpentine as antigorite (a mineral in the serpentinegroup). Eye-visible black inclusions (magnetite) are dis-persed throughout the material. Important trace elementsinclude chromium, nickel, and cobalt. The serpentine,marketed domestically as “Booyo Precious Serpentine,”is fashioned into cabochons, pendants, buttons, beads,and rings. MM

JEWELRY HISTORYElectron microprobe analysis and X-ray diffraction meth-

ods in archaeometry: Investigations on ancientbeads from the Sultanate of Oman and from SriLanka. C. Rösch, R. Hock, U. Schüssler, P. Yule,and A. Hannibal, European Journal of Mineralogy,Vol. 9, 1997, pp. 763–783.

Beads from graves of the Samad Culture (300 BC to 900AD), excavated in Oman, are made of: natural mineralsand rocks (serpentine, talc, and chlorite-containing rocksof local origin, which are soft and can be carved, andalmandine-pyrope garnets believed to be imported fromSri Lanka or India); metal (pure silver and gold, or theseelements alloyed with copper); glass (reddish brown, sodi-um-rich, colored by copper dissolved in the glass matrix);“Egyptian Blue” (a synthetic material produced in Egyptsince the third millennium BC); and synthetic enstatite(formed by heating carved Mg-silicates, such as talc, to1,000°C with a resultant increase in hardness and dura-bility).

Beads from an ancient craftsmen quarter of the oldkingdom of Ruhuna (third to fifth centuries AD), fromrecent excavations in Tissamaharama, Sri Lanka, have afew similarities to those from Oman, particularly withrespect to the garnets, which suggests that there wascommerce between these civilizations in ancient times.However, the potassium-rich reddish brown glass beadsfrom Sri Lanka are distinctive, because they are coloredby tiny droplets of cuprite (Cu2O) and completely lackPbO. This is the first study of its type on beads fromancient Oman and Sri Lanka. AAL

Mineralogy of the Louvres Merovingian garnet cloisonnéjewelry: Origins of the gems of the first kings ofFrance. F. Farges, American Mineralogist, Vol. 83,1998, pp. 323–330.

The garnets in cloisonné jewelry from a burial site inLouvres (North Paris), France, dated to around the fifth orsixth century AD, were examined using the proton-parti-cle induced X-ray emission (p-PIXE) method. This tech-nique allows archeologists, art historians, and others tomeasure the chemistry of such irreplaceable artifactsnondestructively. The 118 cloisonné items examined


were from the tombs of Frankish aristocrats, four femaleand one male; the pieces included brooches, bracelets,and pendants of gold and/or silver construction.

Three types of garnets were identified in the jewelry.Type I, found in the majority of the cloisonnés, is rhodo-lite, with a chemical composition between almandine(iron) and pyrope (magnesium); the source might havebeen South India–Sri Lanka. Type II garnet is pyrope, pos-sibly from Scandinavia, central Europe, or South India–SriLanka. Type III garnet is chromium-rich pyrope, and themost likely source for this rare mineral is Bohemia. SriLanka, then known as Ceylon, was a major source of gar-nets in the early Middle Ages, and these cloisonnés testi-fy to the extent of Ceylonese trade with Europe at thetime. The author proposes that the use of pyrope andrhodolite, rather than the geologically more commonalmandine garnet, in the Louvres cloisonnés may meanthat the Franks had gemological knowledge far moreadvanced than current historical scholarship suggests.

JL

JEWELRY RETAILINGConsumers discover the other ‘C.’ R. Bates and R. Shor,

Jewelers’ Circular-Keystone, Vol. 169, No. 9,September 1998, pp. 144–145.

“Ideal Cut” diamonds are becoming more popular, par-ticularly among the affluent and college-educated,because of increased advertising and publicity. Todaythey account for 5%–7% of diamond sales, up from1%–2% a decade ago. However, there is concern that dia-mond cut is becoming commoditized, thus increasing therisk for deception. Those who overgrade color and clarityare also likely to misrepresent cut. Terms such as “near-Ideal,” “superior” cut, and “fine” cut are confusing to theconsumer, but nonetheless are common in the trade. Ithas also been reported that certain grading laboratoriesare labeling stones as “Ideal” even when they fall outsidecommonly accepted proportions. Such practices may ren-der the term “Ideal” meaningless in the future. MM

Gifts Incorporated. J. D. Malcolmson, JQ Magazine, Vol.77, 1998, pp. 25–34 passim.

Today’s jewelers work in a very competitive market. Notonly must they compete with “traditional” retailers, butthey also must deal with giant mass marketers. One areaof retailing that is not yet saturated is corporate sales. Notlong ago, such an area might not have been very lucrative,but conditions have changed. The austerity that followedthe consumerism of the 1980s has given way to a morecarefree attitude toward corporate gifts of jewelry, eitheras rewards to valued employees or as incentives to cus-tomers.

To succeed in corporate sales, a jeweler must have anorganization that can deliver the product on time and tothe customer’s specifications. Otherwise a special occa-sion could be missed, causing the jeweler to lose a repeat

customer. It is also important to offer products withname value. A Rolex-brand watch, for instance, commu-nicates an extra sense of appreciation to the recipient of acorporate gift. Jewelers who already have a good under-standing of the gift-giving market and products in gener-al will benefit most quickly from such sales. Developingsuch a corporate clientele may be difficult, but therewards—repeat customers of high-end merchandise—can be quite gratifying. JEM-S

It’s a Guy Thing. A. Cardella, American JewelryManufacturer, Vol. 43, No. 8, August 1998, pp.50–54.

Men’s jewelry has historically been one of the most elu-sive markets to tap, but industry forecasters, designers,manufacturers, and retailers agree that the market isenjoying a gradual resurgence. Some of the factors con-tributing to this resurgence are a strong economy that hassparked luxury spending, a more image-conscious man,and a changing economic dynamic in which wives tendto be financially independent, leaving husbands withmore money to spend on themselves.

The key to predicting what men will buy is under-standing why they buy jewelry in the first place. Menshop differently from women: They usually do not buy apiece of jewelry simply because they like it. Salespeopleshould stress the practical function of the piece, not justits appearance. Men are also symbol oriented—oftenmore so than women, notes one forecaster—and will pur-chase jewelry that reflects personal interests such as golf,sailing, or their alma mater. Today’s symbolism alsoextends to spiritual, religious, Gothic, and astrologicalsymbols in men’s jewelry.

The wrist and hand are the focal points of the men’smarket, and bracelets and rings remain the strongest-sell-ing items. Less-traditional items such as earrings are stilllargely unproven, while forecasters predict that necklaceswill surge in the coming seasons. Sales of platinum jew-elry for men are up, with rings and bracelets leading theway. Stuart Overlin

Selling the diamond dream. Diamond International, No.51, 1998, pp. 57, 58, 61, 62.

Adapted from a talk presented by De Beers’s ConsumerMarketing Division director Stephen Lussier, this articlediscusses the company’s approach to consumer market-ing and evaluates both current and future prospects.Central to the De Beers approach is the “diamonddream”: the unique, emotional power of diamond as acultural symbol of prestige, elegance, and love. Becausethe value of diamond jewelry is largely symbolic ratherthan practical (i.e., you don’t need it for transportation ornourishment), the company’s Marketing Division spends$200 million a year maintaining and building the dia-mond dream. These promotions have successfullyexpanded the consumer base for diamonds by developingnew occasions (the diamond anniversary band), attracting


new consumers (young, single Japanese women in theearly 1980s), repositioning products (the evolution of the“Riviera” bracelet into the more casual “tennis”bracelet), and establishing new markets (the emergence ofthe diamond wedding ring in Far East societies).

Three factors make the current environment a chal-lenging one for diamond sales: the decline in the Japanesemarket, the economic crisis in the East Asian markets,and the strength of the dollar. Yet there is optimism,based on: the stability of the Western markets (particu-larly the American market), growth in a region De Beerscalls “Asia Arabia,” promising results thus far in theIndian and Chinese markets, and the enduring desire fordiamonds. It is this “addictive” allure of diamonds thatthe company can always rely on, even when the marketsare having difficulties. Stuart Overlin

Turmoil hits jewellery. Mining Journal, London, Vol.331, No. 8497, September 11, 1998, p. 204.

The economic crisis in Asia has had a major effect ondemand for gemstones and precious metals. In Japan, jew-elry sales for the first six months of 1998 were down 16%from the same period the previous year. Gold jewelrysales were down 18%, and platinum jewelry was down15%. Sri Lanka has also been hard hit as a producer of col-ored stones: Gem exports fell 73% (from 992.6 to 266.3Sri Lankan rupees) in the first five months of 1998 rela-tive to the same period the year before. Seventy percentof Sri Lanka’s gem exports go to Asia. However, theAmerican market remains strong, and exports to theUnited States rose 31.6% in January through May 1998compared to the same period a year earlier. MLJ

PRECIOUS METALSJewellery is now the largest application of platinum.

South African Mining, Gold, and Base Minerals,May 1, 1998, p. 43.

The demand for platinum jewelry is strong and going up.In 1997, more than 2 million ounces of platinum wereused in jewelry. During that same year, consumption“doubled in China and rose 55% in the U.S.” This hastaken pressure off the industry to rely on Japan as themain sales market. An important reason for the successof platinum has been an aggressive marketing campaignby the Platinum Guild International that is based onquality and value rather then price. Scott Rebhun

SYNTHETICS AND SIMULANTSThe death of Kashan. R. Weldon, Professional Jeweler,

Vol. 1, No. 6, July 1998, p. 46.Kashan flux-grown synthetic rubies first appeared about30 years ago and were highly regarded for their fine qual-ity. Nevertheless, the Dallas-based company went out ofbusiness in the mid-1980s. Three years ago, KashanCreated Ruby was revived, but once again it has ceased

production because of competition from now-abundant(especially in smaller sizes) natural rubies from MongHsu (Myanmar), as well as the preference among manu-facturers for the less-expensive flame-fusion synthetics.Over its 30-year history, Kashan produced 44,528 caratsof cut rubies; Mong Hsu churns out 45,000 carats ofrough rubies daily. In addition, there are more than 40other active ruby mines worldwide. AAL

Growing carats. R. Weldon, Professional Jeweler, Vol. 1,No. 1, February 1998, pp. 47–48.

Small amounts of gem-quality synthetic diamonds, mostof which are yellow and in small sizes, are presentlyknown to the trade, but futurists believe that they willbecome more abundant, larger in size, and relatively inex-pensive.

This short article, packed with pertinent informationabout synthetic diamonds, contains predictions primarilyfrom Tom Chatham (Chatham Created Gems), who isgearing up to manufacture gem-quality synthetic dia-monds in the U.S. using Russian expertise. He is strivingfor eventual production from his facilities of 10,000 caratsa month (of J color and SI clarity), and expects that goodsin the 1 ct range will sell for about $500 per carat. AlexGrizenko (Russian Colored Stone Co.), another proponentof synthetic gem diamonds, predicts that commercialgoods will reach 6 ct. At present, his Russian suppliersproduce yellow and “tangerine” synthetic diamonds, andsome green material. Anne M. Blumer

High-pressure synthesis of high-quality diamond singlecrystals. Yu. N. Pal’yanov, Yu. M. Borzdov, A. G.Sokol, A. F. Khokhriakov, V. A. Gusev, G. M. Rylov,and N. V. Sobolev, Diamond and RelatedMaterials, Vol. 7, 1998, pp. 916–918.

Recent techniques in the growth of synthetic diamondsand assessments of crystal defects are summarized. Thesynthetic diamond crystals were grown using the tem-perature gradient method, and X-ray topography was usedto reveal crystal lattice dislocations. The dislocations aresimilar to those found in natural diamonds, and theauthors claim that the dislocations in their synthetic dia-monds take up a smaller volume of the crystal(10%–35%) than defects in natural diamonds. Ultraviolettransparency in the UV spectral regions reached 400 nm,and the synthetic crystals studied had weak absorptioncharacteristics throughout the visible spectrum that aresimilar to those in previously studied annealed synthet-ics. The authors state that synthetic diamonds areincreasing in “quality and purity” as work continues;their size was not reported. JL

TREATMENTSConcern about treatments rises. B. Sheung, Jewellery

News Asia, No. 163, March 1998, pp. 49–52.Treatment of South Seas and Tahitian pearls to improve


their appearance has increased, and industry leaders areconcerned that this may affect consumer confidence.Treatments recognized on the market today includebleaching, polymer coating, dyeing, and irradiation. Thepercentage of pearls being treated is not known; however,it is estimated that as much as 30% of white South Seaspearls are bleached, and up to 80% of golden South Seaspearls are color enhanced. Some in the pearl trade feelthat treated South Seas pearls have a place in the marketbecause the greater availability makes them more acces-sible to more consumers. Others respond that treatmentwill erode consumer confidence and the prestigiousimage associated with South Seas pearls. However, mostagree that disclosure of treatment is vital. The articlementions some techniques for recognizing the varioustreatments. JEM-S

Filled diamond tested by Raman spectroscopic system.C.C. Yuan, China Gems, Vol. 7, No. 2, 1998, pp.53–54 [in Chinese].

Fracture-filled diamonds were studied by Raman spec-troscopy. An argon ion laser beam (0.005 mm in diame-ter) focused on filled fractures revealed two types of fill-ing material. One, lead glass, shows a broad Raman peakin the range of 830–930 cm-1. The other, believed to beresin, gives a series of peaks in the 1100–3000 cm-1 range.This article illustrates that Raman spectroscopy is a pow-erful technique for identifying materials used to fill dia-monds and other gemstones. Taijin Lu

MISCELLANEOUSGreen mining. S. Frazier and A. Frazier, Lapidary Journal,

Vol. 51, No. 9, December 1997, pp. 45–48, 50, 64.In the past, mining technology was concerned solely withretrieving minerals from the ground at a profit, withoutmuch regard for environmental matters. Gold mining, forexample, once polluted the environment of the westernUnited States with mercury, which was used to recoverthe gold from the ore. In addition, the hydraulic methodsused for gold mining destroyed California hillsides.Copper mining at Butte, Montana, has dispersed danger-ous heavy metals into the atmosphere, soils, surfacewater, and groundwater. Such practices are no longer tol-erated in many countries, and all future mining must beenvironmentally friendly, even though this process maybe expensive, time consuming, and difficult to engineer.These problems are now easier to solve, however, becauseof new mining technology and a better understanding ofmineral deposits.

“Green mining” (i.e., environmentally responsiblemining) is currently being practiced at many locations inNorth America. The article cites as examples a gold andmyrickite (a red cinnabar–opal–chalcedony mixture) minein northern California, and the Sweet Home rhodo-chrosite mine in Colorado. The mining of gems, crystals,and fossils—like that for metals and all other earthresources—is now commonly accompanied by a demandfor environmental protection. MD

Shipping safely. C. Marandola, American JewelryManufacturer, Vol. 43, No. 8, August 1998, pp. 56,58–61.

Jewelry is intrinsically vulnerable to loss during shipping,but precautions taken before a package is sent can controllosses and keep insurance rates down. This article detailsfour specific steps, gleaned from industry experts:

(1) Establish internal procedures. A chain of custody,with as many people involved as possible, simplifies pin-pointing where the loss occurred. The following shouldbe documented: description of the items, value, destina-tion, type of packaging, and carrier. Instruct employeesnot to share even casual information with pick-up dri-vers.

(2) Package to minimize theft. Use ordinary-lookingbut sturdy brown or white cardboard boxes, no smallerthan an adult shoebox, securely sealed with gummedreinforced paper mailing tape, pressure-sensitive tape, ortamper-evident tape. The box should be new; used onesare easier to tamper with. Placing a smaller box within alarger box reduces loss from slit packages. Include anitemized packing slip inside the box and send a copy sep-arately. The labeling on the package should not denotejewelry or precious metals (use initials rather than com-pany names). Adding weight to the box diverts suspicionof light and valuable contents. Use labels that cannot beeasily replicated and affix them well.

(3) Follow consistent shipping guidelines. Researchthe shipping company’s reliability and hiring practices.Avoid shipping to known jewelry zip codes (47th Street inNew York and Hill Street in Los Angeles). Armored truckand first-class registered mail are safest. Services such asUPS, FedEx, and Express Mail are riskier because they canbe targeted by thieves at a central point. Also, shippingearly in the week means packages will not have to sit ina warehouse until Monday morning.

(4) Prepare for loss. This section addresses insurancelimitations and extent of coverage through shippers andinsurance agents. As a general rule, insurance shouldcover 110% of the item’s value, plus freight and inciden-tals. Carole Johnson


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