Download - Diamonds: Beauty and Brawn Carl Wozniak Graduate Gemologist (GIA) Northern Michigan University
Diamonds: Beauty and Brawn
Carl Wozniak
Graduate Gemologist (GIA)
Northern Michigan
University
The allure of diamonds• The world’s love of diamonds
started in India.• Romans set uncut diamonds in
jewelry• By the 1400s, diamonds had
become fashionable in Europe.
Roman ring, 4 A.D.
Why the allure? Diamonds are
cherished because: They are rare They are durable They are beautiful They have value They are expensive to
mine and cut
Cutting Diamonds are
extremely hard. In order to cut
them, you have to use other diamonds.
Rough diamond
Diamondanatomy
A round brilliant cut diamond has either 57 or 58 facets.
What makes diamonds sparkle? A polished diamond’s beauty lies in a
complex relationship with the light around it.
Facets on the stone reflect light externally and internally.
What makes diamonds sparkle? We see this interplay between light and
the diamond in three qualities Brilliance- the degree to which light from
within the stone returns to our eye Fire- the play of colors from the refraction
of light within the stone Scintillation- the bits of light that flash as
the stone is moved
Brilliance
In brilliant stones, much of the light that enters leaves through the crown. Less brilliant stones result when light leaks out the pavilion.
Fire
Fire, also known as dispersion, is the color play within a diamond caused by refraction of light in the stone.
Scintillation
Scintillation is caused by light reflecting off the stone’s facets.
Grading diamonds
Why grade diamonds? Diamond grading: Makes it possible to
discuss diamonds simply and concisely;
Helps you compare stones;
Helps identify quality.
Grading diamonds
The 4 “C’s” Color Clarity Cut Carat weight
Color
While there are fancy colored diamonds that can be extremely expensive, typical diamonds increase in value as they get closer to colorless.
The currently used grading scale was developed by the Gemological Institute of America
A, B, C were not used to prevent confusion with existing scales.
Hope Diamond45.52 ct., VS-1,Fancy deep grayish blue
Rule of thumb Colorless face up and face down
D, E, F Colorless face up, nearly colorless face down
G, H, I, J Faint yellow face up, faint yellow face down
K, L, M Very light yellow face up and face down
N, O, P, Q, R Light yellow (substantial) color face up or down
S, T, U, V, W, X, Y, Z
Color Color is very difficult to judge in
mounted stones Proper lighting is essential
Clarity Most diamonds come with
some amount of “junk” inside them. We call these inclusions.
Scratches and other surface imperfections are called blemishes.
Before the 1950s people in the diamond industry had no way to accurately describe a diamond’s features so that everyone understood them in the same way.
Clarity The GIA’s diamond grading system was
developed in 1953 to give professionals a way to evaluate diamonds and communicate quality to others.
Clarity Five clarity factors that determine the grade of
a diamond Size of inclusion Number of inclusions Position of inclusions Nature of inclusions Color or relief of inclusions
The clarity grade is not based on the sum of everything in the stone, but is based on the largest and most visible characteristics.
Typical Inclusions
Clouds
FeathersCrystals
Needles
Pin points
Clarity Grades Flawless (F) stones are exceedingly
rare and never worn.
Millenium Star, 203.04 ct., D, Flawless
Flawless stones have no visible inclusions under 10 X magnification, and there are no blemishes on the stone’s surface.
Clarity Grades Internally Flawless (IF) diamonds have
the potential to become flawless stones.
Internally flawless stones have no visible inclusions under 10 X magnification, but there are blemishes on the stone’s surface.
Clarity Grades Very Very Slightly (VVS) included
diamonds
Contain minute inclusions that are extremely or very difficult for a skilled grader to see under 10 X.
•VVS1= extremely difficult to see face up (one or two pin points)
•VVS2= somewhat easy to see
Clarity Grades Very Slightly (VS) included diamonds
Contain minor inclusions that are difficult to easy for a skilled grader to see under 10 X.
•VS1= difficult to see inclusions
•VS2= somewhat easy to see
•Typically small crystals or feathers near the edge.
Clarity Grades Slightly Included (SI) diamonds
Contain noticeable inclusions that are easy or very easy for a skilled grader to see under 10 X.
•SI1= easy to see inclusions
•SI2= very easy to see. Eye visible.
•Typically crystals, feathers or clouds centrally located.
Clarity Grades Included (I) diamonds
Contain obvious inclusions to a skilled grader under 10 X.
•I1= quite visible inclusions
•I2= easily visible
•I3= extremely visible. Affects the stone’s durability.
I-2
I-3
Cut Diamonds can be cut
in many different shapes, but this is not all we mean by “cut.”
Cut refers to not only the shape of the diamonds, but its proportions and finish, factors which determine the sparkle of the diamond.
Cut Round brilliant cut diamonds have been
studied the most. They are the most common The proportions are relatively consistent
Cut
Cut
Misalignment of facets, misshapen facets, and pointing problems go hand-in-hand. Where you find one, you’ll usually find the others.
Carat weight Diamonds weight
is measured in carats. 1 ct. = 1/5 gm. 1/100 ct. = 1 point
Carat weight Rule of Thumb 1
All other things being equal, the bigger the stone, the more expensive it is.
Carat weight Rule of Thumb 2
Cost jumps dramatically at “magic sizes.”
The care and feeding of diamonds
Diamonds have a high affinity for grease. Rough diamonds are actually sorted using grease tables.
Grease changes the refractive index of the stone, causing light to leak out the pavilion.
The care and feeding of diamonds Use an old toothbrush and soapy water
to clean under the stone.
•Can also use ultrasound or steam
•Keep gold jewelry away from chlorine bleach.
Synthetic diamonds Synthetic diamonds are becoming more
common, but they are usually small stones, yellowish stones.
Diamonds are made under temperatures of about 2,200º F and 50,000 atmospheres.
Synthetic diamonds
Cremated remains can be made into diamond.
Common Diamond Simulants Cubic Zirconium (Zircon Oxide)
CZ has slightly less brilliance or sparkle than a diamond and more fire or flashes of color
CZ also comes in many colors.
Common Diamond Simulants Telling CZ from diamond
About 75% heavier than diamond CZ is softer, you see this in abraded facet
junctions Orange pavilion flash Usually flawless Many colors Thermal conductivity
Common Diamond Simulants Moissanite- Silicon
carbide Has inclusions and
color differences Similar thermal
conductivity Very hard Slightly lighter than
diamondMoissanite has a lot more fire than diamond.
Common Diamond Simulants Moissanite- Silicon
carbide But, moissanite is
strongly doubly refractive
A little knowledge will make you a better consumer.
You’re invited to clean and examine your own stones.