retrospective views on the identification of the hpht

Retrospective views on the

identification of

the HPHT treatment

Centenary Diamond 273.85 ct , courtesy of De Beers

J-P. Chalain Gem-A 2015

Layout

1. Five introductive refreshers

• first mention of the ‘HPHT’ term in gemmology

• LKI & GE press release ‘an undetectable new treatment’ (1999)

• what is the HPHT treatment?

• effect of the HPHT treatment on type Ia diamonds

• effect of the HPHT treatment on type II diamonds

2. Chronological overview of the ID of the HPHT treatment

• of type II diamonds (9 slides)

• of type Ia diamonds (6 slides)

• SSEF’s collaborations

3. Three conclusions

Refresher 1: in 1997, THE very first mention of “HPHT”

in a gemmological paper, Mark Van Bockstael

© SSEF

• Colour: greenish yellow

• N3, thus type Ia

• H3

• « HPHT »

Refresher 2: In 1999, THE LKI & GE press release,

T r a d e A l e r t ( f r o m R a p a p o r t , M a r s 1 9 9 9 )

L a z a r e K a p l a n ( L K I ) h a s c o n c l u d e d a t e n y e a r e x c l u s i v e w o r l d w i d e

m a r k e t i n g a g r e e m e n t w i t h G e n e r a l E l e c t r i c C o r p o r a t i o n ( G E ) a n d

w i l l b e g i n m a r k e t i n g d i a m o n d s t r e a t e d b y a n e w s e c r e t G e n e r a l

E l e c t r i c p r o c e s s i n A p r i l .

T h e i r r e v e r s i b l e p e r m a n e n t p r o c e s s c a n

s i g n i f i c a n t l y e n h a n c e t h e c o l o r a n d b r i l l i a n c e o f s e l e c t t y p e s o f

r o u g h a n d p o l i s h e d d i a m o n d s .

A m a z i n g l y , L K I s a y s t h e t r e a t m e n t i s u n d e t e c t a b l e a n d w i l l r e m a i n

u n d e t e c t a b l e .

The PR keeps secret: the treatment and the type of diamond.

So, gemmologists did not link this press release with the announcement of Mark Van

Bockstael in 1997 and therefore, they did not immediately foresee the HPHT treatment.

The reason why GE & LKI announced that the treatment will remain undetectable will be

given in the conclusion.

Refresher 3: What is the HPHT treatment?

© SSEF

HP: 60 kbar,

HT: 1’200°C.

Outdated HPHT press (for sale!), Inreal, St Petersburg

The HPHT treatment removes the brown colour of any type of diamond, type I and type II

The HPHT treatment has the same effect on natural diamonds and synthetic diamonds.

Refresher 4: Effect of the HPHT treatment of type Ia diamonds

(after a study made in 2001 at the SSEF with Bleuler AG)

Roughs (ref. 1 à 10) before treatment

When it applies on diamonds OF ANY TYPE,

the HPHT treatment removes any brown colour

(& possibly green).

On a type Ia diamond, the final colour is either:

Yellow

greenish yellow

Yellowish green

Orangey

Roughs (ref. 1 à 10) after treatment

When it applies on diamonds OF ANY TYPE,

the HPHT treatment removes any brown colour

(& possibly green).

On a type II diamond the final colour is either:

Colourless

Pink

Blue (IIb)

Refresher 5: Effect of the HPHT treatment of type II diamonds

(after a SSEF study made in 2002 with Branko Deljanin)

Two parts of the same CVD synthetic diamond (type IIa)

LEFT: before treatment / RIGHT: after HPHT treatment

© SSEF

1999: Prof. E. Fritsch sent a publication to SSEF Collaboration with the University of Nantes

Joe C.C. Yuan’s publication

He comments:

” Check with your Raman,

there’s something we don’t understand.”

From Yuan’s publication, p.27

1999: SSEF extends its collaboration with DTC Research

Room t°& extended Raman spectrum, showing PL features

2 publications: Detection of GE POL diamonds: steps 1 & 2 (in J. of G. & Revue de l’AFG)

First low t° PL spectrum, after DTC Research advice SSEF Raman probe

with its cryogenic cell

SSEF shows the first PL spectra made with a Raman spectrometer

1999: SSEF build the first type II spotter

(with Prof. Fritsch & Prof. H. Hänni)

Winter 1999: Birth of the SSEF Spotter for selecting the

following at the Gidish company:

• 40 colourless type II untreated diamonds

• 20 brown & pink type II untreated diamonds

Fall 1999, a G&G’s publication

reveals that all GEPOL diamonds are type II

Collaboration with Horovitz & Totah and Gidish, Geneva

IR spectrometer: 100’000 US$, in 1999

March 2000: Breakthrough on the ID of HPHT treated type II

Summary of the SSEF results sent to DTC Research for the blind test

consisting in 3 series of 6 type II diamonds HPHT treated and untreated

March 2000: Rapaport press release:

« SSEF can identify GEPOL diamonds »

April 2000: DTC Research send to SSEF a

series of 18 type II diamonds (mixed HPHT

treated and untreated) for a blind test.

May 2000, De Beers congratulates

SSEF for its work on the identification of

HPHT treated diamonds of type II.

Mr. Oppenheimer, congratulates SSEF

SSEF receives 21 GEPOL

on loan from 12 CIBJO labs & GGL.

Collaboration with all CIBJO laboratories

Spring 2000: DTC publishes in G&G its first results on the identification

of the HPHT treatment of type II diamonds (featureless spectra, ratio NVo/NV-)

Summer 2000: SSEF publishes in G&G an additional criterion, FW(NV-).

NOTE:

In 2000, DTC & SSEF agreed

to not reveal the GR1 criterion

because a possible secondary

treatment by irradiation would

make the identification of the

treatment even more complicated.

2000: DTC & SSEF Publications

2000: About the PL features of secondary treated diamonds

The low t°PL spectrum of HPHT type II diamond

does not show a GR1 (heat sensitive) &

may show NV peaks

The low t°PL spectrum of untreated type II

diamonds ( brown and colourless) shows a GR1

The low t°PL spectrum of HPHT & irradiated

(secondary treatment) type II shows again a GR1

(effect of irradiation)

After D. Fisher works in 2008, it seems

now reasonable to interpret the high

value of FW(NV-) as being simply that of

the original brown diamond value (before

treatment).

- FW (brown) > FW (colourless)

- FW[GR(HPHT)] > FW [GR(nat.)]

2000: About SSEF Publication

Note about the value of the FW(NV-) published in G&G Summer 2000

2003 & 2004: Divulgation of unpublished findings

to other laboratories

SSEF organizes two DTC/SSEF meetings in Basel for sharing the

following information with GIA, IGI, HRD & GGL.

The following data were shown & explained:

Values of FW(GR1), FW(NV-), ratio NV-/NVo for: • Untreated type II,

• HPHT treated type II

• Undeterminable type II and

• Secondary treated type II (HPHT plus irradiation)

Importance of a long-term referenced calibration of the Raman

spectrometer (sharing parameters)

Presence of the 648 nm PL peak in untreated type IIb

What about type Ia diamonds?

2004: Uncertainties on type Ia HPHT treated diamonds

On the Museum archive document

one can read: H 5222, rough

diamond yellow/green, 0.224 gr

(1.12 ct)

The H 5222 diamond shows

a colour similar to that of

HPHT type Ia diamond

The H5222 diamond was offered

in 1907 to the Natural History

Museum of Vienna by her

Majesty, the Emperor Franz

Joseph the First

© SSEF

© SSEF

collaboration with the Natural History Museum of Vienna

Ntotal: 93.0 ± 7.4 ppm

A : 47.1 ± 2.9 ppm

B : 43.1 ± 4.3 ppm

C : 2.8 ± 0.2 ppm as seen in HPHT

treated treated diamonds!

Decomposition of the

single-phonon region (ref. H 5222)

0

2

4

6

8

10

12

14

3997851 1711 5561 9422 3282 7133 0993 4853 8704 2564 6425 0285 4135 799

Wavenumbers

Ab

so

rp

tio

n c

oe

ffic

ien

t

H5222 FTIR spectrum

© SSEF

© SSEF

© SSEF

FTIR study


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

800770740710680650620590560530500470440410380350320

wavelength (nm)

Ab

s

H 5222

H 5222 low t° UV-vis.

absorption spectrum

A very strong H3 centre

as seen in HPHT treated diamonds!

© SSEF

© SSEF


UV Vis study

H 5222

0.00

0.01

0.01

0.02

0.02

0.03

0.03

0.04

1 010 1 002 994 986 978 970 962 954

Wavelength (nm)

Ab

s

H 5222

Thus, the H 5222 shows both C centres, a very strong H3 centre & a H2 centre (986 nm).

In 2004, by lack of studies of natural yellow green diamonds, the presence of these features

which are present in HPHT treated diamonds of type Ia were considered as characteristics

for the HPHT treatment.

Conclusion:

In 2004, there was a need for additional differentiation criteria (FW(B’) in 2009)

near-IR study

H2 (as seen in

HPHT treated

diamonds)


The FW(GR1) for untreated type IIb

diamonds showing a 648 nm PL peak

have an unusually high value:

FW(GR1) > 1,80 meV (up to 3,00 meV!)

This high value is that usually expected for

a HPHT treated diamond that has been

subjected to a secondary treatment.

Hence the importance of checking for the

presence of the 648 nm peak when

measuring the FW(GR1)

2007: study of the 648 nm PL peak

Results presented at the Diamond Conference, July 2007

16%

69%

15%

17%

67%

17%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

<0.60 0.61 - 1.30 1.31 - 1.80 >1.81Stress as measured by the width of the GR1 (in meV)

Distribution of stress values for type II of D colour:

With a 648 nm PL peak Without a 648 nm PL peak

2007: study of the 648 nm PL peak

Results presented at the Diamond Conference, July 2007

2009: Study of FW(B’) in type Ia HPHT treated diamonds

Platelets (B’) are giant groups of interstitial carbon atoms formed as a by product

of the nitrogen aggregation process (Woods, 1986)

In 2001, when studying the before and after HPHT treated diamonds of type Ia,

SSEF noticed that FW(B’) was increasing after treatment.

But natural yellow green diamonds are rare…

… thus, SSEF & DTC Research has ploted their samples on

a joint diagram for a better statistical representativity of their results.

2009: Study of the FW(B’)

Much less uncertainties on the ID of HPHT treated diamonds of type Ia

First conclusion, 1 of 3

1. Collaboration was an efficient solution for challenging

the identification of the HPHT treatment

True thanks go to: Mark Van Bockstael

Joe C.C. Yuan

University of Nantes (Prof. E. Fritsh),

DTC Research (now De Beers Technologies)

P. Spear, D. Fisher, M. Cooper & S. Lawson

Natural Historic Museum of Vienna (V. Hammer)

CIBJO Labs (more than different 10 labs)

David Goal (Gidish), Ronny Totah (H. & T.)

Untrue thanks go to: GE & LKI : from whom SSEF received 22 pages of fax explaining that they will send

HPHT treated samples which they never sent to SSEF - 3 lost months of research!

a. Contribution to the identification of HPHT treated type II diamonds Absence of GR1

Measurement of FWHM(NV-)

Presence of the PL 648 nm peak increases the values of FWHM(GR1)

b. Contribution to the identification of HPHT treated type Ia diamonds Demonstrated by the study of the H5222 diamond from the NHMVienna

Measurement of the FWHM(B’)

c. Other fundamental contributions to the identification of the HPHT treatment David Fisher (type II)

David Fisher (understanding the origin of the brown colour),

Alan Collins (understanding the HPHT treatment when it applies on type Ia diamonds)

Tom Moses & Matt Hall (1st description of pink & blue type II treated HPHT diamonds)

Second conclusion, 2 of 3

In 2003, SSEF took every legal mesure

to ensure that this patent will not apply to

Switzerland.

Last conclusion, 3 of 3 (probably the most spicy one)

Thank you for your attention

« Centenary Diamond »

NOT a HPHT treated diamond

retrospective views on the identification of the hpht

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