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A
diamonds color grade tells how much color is in the
diamond. A diamond that is totally colorless is worth
more than a diamond with a hint of color. Color
grades range from a colorless “D” grade up to a
yellow/brown color “Z”. Any diamond with more
color than "Z" is graded as "Fancy Color". Fancy
Colored diamond and are valued lower than white diamonds
of the same cut and carat.
The following chart illustrates the color
characteristics of the diamonds from colorless to
yellow/brown.
Color grading is done by placing
the diamond face down and comparing them to master
stones under special lighting. Emerald and Asscher
cuts show more color than ideal cuts such as round
brilliant. Some diamonds may have fluorescence,
and is not graded under Color. This is made easily
visible under an ultraviolet light source such as a
black light used in special effects. Diamonds with
fluorescence will glow under an ultraviolet light.
Fluorescence can be faint to very strong, and the most
common fluorescent color is blue. As blue is the
complimentary color to yellow, the most common tinted
color in diamonds, blue fluorescence can make yellowish
diamonds look white or colorless.
There are many methods of enhancing diamond colors. Some
are to whiten white diamonds and others are to enhance
the color with diamonds with not-so-good color. At
JewelryOction.com, we use color enhancement to create
fancy colored diamonds only. We do not use any
methods to raise the grades of white diamonds. Such as
enhancing a “G” color diamond to “E”. The
different methods we use to enhance the color in our
diamonds are HPHT, Irradiation and Surface Enhancement.
All our items are clearly labeled as Enhanced on our
item description.
High Pressure, High Temperature (HPHT)
HPHT is a process developed by
General Electric in 1999 to color treat diamonds.
This process puts over 60 kbar (nearly 1,000,000 psi) of
pressure on the diamond at around 1400°C (2550°F).
Diamonds treated with HPHT can transform into many
colors including to pinks and blues. HPHT can also
be used to create white diamonds, however
JewelryOction.com will only use this process to create
fancy colored diamonds. This treatment is
permanent and will not be affected by cleaning or heat
from setting repairs.
Irradiation (IRR)
Irradiation treatment involves
exposing the diamond to electromagnetic rays to release
electrons from their normal location to a more desirable
location changing its color. Neutron bombardment
and electron bombardment are the two main irradiation
methods practiced today. Diamonds treated by
irradiation produce many brilliant colors such as green,
yellow, blue and reds. This color treatment is permanent
and will not be affected during cleaning processes.
However, blue or green enhanced colors could change to a
yellowish color if high heat, 300°C (572°F) or more, is
used during setting repairs.
Surface Enhancement (SE)
Surface Enhanced diamonds are
chemically treated to change the color of a diamond to
Brilliant colors. This is done by coating the diamond
surface with a metal halide. A similar technique
used to coat some camera lenses that create the blue
reflection. This method can produce vibrant pinks
and cognac reds. Care should be taken with surface
enhanced diamonds. The coating can wear out during
heavy cleaning or heat from setting repairs.
Heat Treatment (HT)
Heat Treatment or 'annealing' is
done using a combination of chemicals (beryllium, borax,
lead, tantalum) and heat to change the diamond's color.
Heating or "cooking" the diamond is done at temperatures
ranging from 450ºC (842°F) to 1850ºC (3362°F) for 2 to
12 hours or more. We only use this process to
create our black opaque diamonds. To check if a
diamond has been heat-treated, one way is to look for
the presence of small fractures within the stone that
appear around natural mineral inclusions. This
treatment is permanent and will not be affected by
cleaning or heat from setting repairs. |
