Treatments Used to Improve the Color of Diamonds
Color affects diamond prices
A diamond's color—or lack of color—is one of the
components that affects its value. Diamonds with the least
amount of color, graded D, E, and F, are rare and command higher
prices than diamonds with yellow or brownish tones.
On the other end of the spectrum, vivid, fancy
color diamonds are even more unique, with price tags to reflect
their rarity. So it's no wonder that the jewelry industry has
developed methods to turn ho-hum diamonds into the show-stoppers
that the public demands.
Turning yellow and brownish diamonds into
gemstones with more visual appeal isn't a new idea, but some of
the technology used to accomplish it is. Like other diamond
treatments, only some of the methods used to enhance the stones
Coatings & Other Color Tricks
Coatings applied to change a diamond's color are not permanent
and are nearly always done to deceive the buyer.
Irradiation & Heat Treatment
Irradiation, followed by a high heat treatment, can turn brown
and yellow diamonds into fancy colored diamonds--greens, vivid
yellows, blues, purples, reds and other colors. The color is
usually permanent, but could possibly change if high heat is
used during setting repairs.
- Natural fancy colored diamonds are
expensive and out of the reach of most buyers. A certificate
from a respected grading lab should accompany all fancy
colored diamonds that are marketed as natural.
- Question the ethics of anyone who
attempts to sell you a natural fancy colored diamond
for a bargain price.
- Treatment-produced fancy colors are
affordable, and allow more of us to own a brightly colored
diamond. They should not be considered an investment. Buy
one because you love it, not because you think you can sell
it for a profit later.
- Ask the jeweler for care instructions
when you buy an irradiated fancy color diamond.
High Pressure High Temperature Treatment (HPHT)
HPHT was first used to turn yellowish diamonds into fancy
colored gemstones, but now it's also used to transform some
brown diamonds into colorless diamonds that can be sold for a
much higher price.
Some companies claim HPHT isn't a treatment at
all, calling it a technique that finishes the job nature
started. That attitude, and the fact that the process is
difficult to detect, has made HPHT a controversial topic.
General Electric is producing colorless
diamonds, called Bellataire, from type IIa diamonds that are
nitrogen-free. The company has applied for a patent on the
process used to transform the stones. On their Bellataire Web
site, GE states:
"BELLATAIRE Diamonds are extremely rare Type
IIa diamonds that were originally crystallized without color
and were destined to become extraordinary gems. During their
journey to the surface of the Earth through volcanic pipes,
though, these crystals were subjected to intense heat,
tremendous pressure, and explosive turbulence. These
conditions caused some molecular misalignment in these
crystals, resulting in a brownish color and internal
GE's position is that the process they use
restores diamonds to their colorless state.
Gemological Institute of America (GIA) grading
reports now indicate when HTPT treatments are detected by
stating "HPHT Annealed" or "Artificially Irradiated" in the
Origins portion of a report.
- Only diamonds that are laser-inscribed
with the words "HPHT PROCESSED," "IRRADIATED," or a specific
registered name are graded.
- GE uses a registration number and the
letters "GE POL" to inscribe their diamonds.
- There have been instances where inscribed
lettering has been removed before a diamond was submitted
HPHT will continue to be a controversial
topic, with grading labs trying to perfect ways to detect the
always-improving process so that consumers can receive full
disclosure about the diamonds they purchase.
Should you purchase an HPHT diamond? You're
the only one who can make that decision. The diamonds are
definitely gorgeous, but choosing between altered and natural is
a very personal decision.
A few facts about HPHT Diamonds:
- HPHT is permanent.
- The Federal Trade Commission (FTC)
requires that HPHT be disclosed.
- Most HPHT diamonds are over .5 carats.
- HPHT diamonds should cost less than
similar natural diamonds.