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Myths and Truths of Treatments & Synthetics
If the supply of gems were limited to those specimens that are naturally attractive, they’d
be so expensive that most of us could never own one. Therefore, many gems are
treated. A treatment is any processing such as heating, oiling, irradiation, waxing,
staining or bleaching which alters the color of clarity of a gem.
The word enhancement is often used toe mean treated. However, it has a broader
meaning. Enhancement also refers to the faceting and polishing of a gem. In addition, it
sounds more positive, which can lead buyers to believe that treatments are always
beneficial when they often are not. If stones are improperly heated, for example, they
may become brittle, causing them to chip or even shatter more easily. Some gems labs
use the term “enhancement” on reports to refer to routine treatments which are already
accepted in colored gems. Treatment is reserved for unacceptable treatments. This
policy has the effect of turning treatment into a negative term when in fact it is a neutral
term by dictionary definition. In any case, a treatment may be good or bad. Treatments
or enhancements of any kind should be judged on which treatment is being used and
how it is performed. It makes more sense to simply state on lab reports the type of
treatment the gem has received. The buyer can then determine if that was appropriate
for the type of stone in question.
Heat Treatments
For centuries, gems have been heated to improve their color. However, in the past 30
years, heat treatment has been conducted on a wider scale and at much higher
temperatures, 2900 F / 1600 C and more. Besides lightening or darkening the color of a
stone, heat cam improve its clarity. Unless a receipt of lab document states otherwise,
you should assume that the following gemstones have probably been heat treated:
aquamarine, carnelian, ruby, sapphire, tanzanite, pink topaz, green tourmaline and
green zircon.
Heat treating is widely accepted because it’s a continuation of a natural process and it
causes a permanent improvement of the entire stone. From the standpoint of value, it
does not matter if the stones have been treated or not as long as the color is permanent.
The overall quality of the stone determines the price. However, a premium is usually
charged for high-quality untreated stones that come with a lab report stating that the
stone has not been altered.
If heat treatment is not handled properly, stones may become brittle and therefore less
durable. When buying a ruby or a sapphire check to see if the stone has severe
abrasions and pits. Because of their hardness, such stones should normally provide
excellent wear. However, if the stone you’re considering has never been work and shows
flaws on the facet edges, it may not have been heated properly.
Irradiation
Various types of radiation are sued to intensify or change the color of certain gems.
Gamma rays form a cobalt or cesium source are the preferred irradiation agent because
they don’t induce radioactivity. Pink tourmaline is one example of a stone that is
commonly treated with gamma radiation to intensify its color. Untreated pink and red
tourmaline owes their color to natural radiation. The gamma treatment speeds up the
natural process of making colorless tourmaline crystals red or pink. The strength of the
color can be a measure of the dose of radiation the stone received naturally and/or
through treatment. The color is relatively stable, but strong heat may sometime cause it
to fade. Fortunately, irradiation treatment will bring back the color. Irradiation pink and
red tourmaline is free of radioactivity because the gamma treatment does not change the
nucleus of the atom. Instead what happens is the out electrons are moved into different
positions creating color centers which change the way the stone absorbs light.
Topaz is another example of a stone that routinely irradiated. But in order to obtain the
desirable intense blue color, the irradiation is done by one of three different processes.
In cases, colorless topaz is irradiated in a high-energy electron-beam linear accelerator
and/or nuclear reactor, which usually turns it brown. The topaz is then heat-treated to
produce the stable blue color. The irradiation uses much higher energy levels than for
tourmaline. This can result in a change to the nucleus of the atoms of the impurities in
the topaz and cause them to become radioactive. It may take days or years for this type
of radioactivity to decay. There have been a few isolated cases where blue topaz was
sold before it was safe, particularly in the 1980’s. We have learned a lot since then and
many countries regulated the processes. The United States has the strictest
requirements. When suppliers of blue topaz guarantee that their stones from a licensed
facility that’s in compliance with standards set by the Nuclear Regulatory Commission,
you need not worry about radioactivity in topaz.
Only certain other gems may be enhanced with irradiation. These include: Yellow beryl,
Smoky quarts, Yellow or Orange Sapphire (since irradiation fades too much, more is
heat treated than irradiated), green, blue, yellow or champagne diamonds and black or
dark color pearls.
Fracture Filling
When surface-reaching fractures in gems are filled with an appropriate substance, they
are less noticeable and the overall color and transparency may improve. Emeralds
typically have small surface-reaching cracks to they’re commonly filled with oil, wax or
epoxy. Unfortunately, the filling can evaporate and maybe sometimes leave a white or
brown residue. This is not a major problem if the stone has been oiled because the
stone can be cleaned out by repeated immersions in solvent. Afterwards it can be re-
oiled to look as good as when bought. Some hardened epoxies, however, can be difficult
to extract. Therefore fillers which are easy to remove and a stable as possible tend to be
the preferred types of fillers for emeralds. Ruby is another stone that may be oiled or
filled with epoxy when surface-reaching cracks are present. However, unlike emerald
oiling, ruby oiling is not accepted by the trade.
Glass-like filling may also be present in some rubies. During heat treatment, a borax
solution used on the stones can melt and form a glass that seeps into fractures and
cavities. It’s less accepted than heat treatment, but more accepted than ruby oiling. This
process improves the stones’ appearance and can improve the stone durability since the
fractures are healed shut. The less filling the more desirable the gem and there should
be documents indicating the extent of the filling process. It is often described as minor,
moderate, significant or none.
Staining
Rubies, emeralds, jade and other stones with small surface cracks are occasionally dyes
with colored oils, epoxies or stains. This technique is used most often on low quality
stones. Some precious stones such as lapis lazuli, chalcedony and agate are porous
enough to accept a stain and often treated in this manner. Black onyx is simply stained
chalcedony. Stained lapis and chalcedony are accepted by the trade, but this is not the
case for rubies, emeralds and jade. Treating stones this way is a practical means of
making lower grade material look better. Unfortunately, these stones are often sold with
the intend of fooling buyers and has therefore become a deceptive practice.
Diffusion
This treatment is most often done to sapphires, rubies or topaz to turn pale or colorless
stones blue, orange, yellow, red or green. It may also be used to form a star. Coloring
agents like titanium, chromium and beryllium are diffused into the stone. For example,
pale stones are a packed in chemical powders which impart color and then heated to
2900 F / 1600 C and above until a thin layer of color is diffused into the surface of the
gem. Diffusion is relatively new (about 30 years old per patent records) and is not yet
very well accepted by the trade. However, it’s becoming more prevalent and for some
stones, even popular. Unfortunately, this treatment can also be used to deceive. In 2002,
gems labs discovered that much of the orange sapphire being released was diffusion
treated. Topaz is one of most commonly diffusion treated stone. The color is permanent,
but often remains only in the first millimeter of the stone. It is possible to chip the stone
and reveal its otherwise pale interior. For any gem purchase, ask if it has been diffusion
treated.
Coatings
Romans used to wax their marble statues to hide cracks and to make the surface look
shiny. Today gems are waxed and plasticized for the same reasons. One coated gem
that was recently introduced to the market is “mystic topaz”. It has a color-play of
green/purple or red/yellow which is the result of a special coating. It retails for about
$10/carat. While very popular (and profitable for jewelry counters) as more people
understand that these coatings are very fragile and short lived, they are moving away
from such stones.
Summary
The treating of gemstones is one of the most controversial subjects in the gem trade.
Most gem and jewelry organizations now encourage their members to disclose
treatments; unfortunately gem suppliers don’t always tell jewelers how they stones have
been treated, so retailers may not have adequate information to pass on to customers.
Detecting treatments can also be very difficult or impossible for even the world’s
foremost gem laboratories. That said, a laboratory is still your best bet to determine a
stone’s true nature.
Jewelers and jewelry salespeople should be able to give you general information about
treatments. They should know, for example, that most emeralds are oiled to improve
clarity and they should tell you this. Additionally, they should be able to explain why a
stone was treated and give you special care instructions where necessary. If you don’t
know a salesperson, it’s had for you tell if they are knowledgeable and ethical. One way
of learning something about the character of sellers is to ask what kind of treatments
their stones have received. If they are candid and informed, this is a good sign.
Reputable salespeople give their customers practical advice and basics facts about
treatments. As with the jewelry investment, you are also making an investment in the
relationship with you jeweler. A good relationship, in the long run, may be worth as much
as the jewelry itself.
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