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GEMSTONE TREATMENTS
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Enhancement is defined as any process other than cutting and
polishing that improves the appearance (color/clarity/phenomena),
durability, or availability of a gemstone”
Gemstones
rarely reach the customer in their rough, natural state. Perhaps the
most basic "enhancement", is the faceting and polishing of
a gemstone in order to enhance its beauty and wearability. This
enhancement, of course, does not have to be disclosed because the
gem's outward appearance makes it obvious that the process has taken place.
Other
treatments may not be so obvious or quite so durable. Depending upon
the material, some gems might be subjected to heating, irradiation,
diffusion, filling of surface-reaching fractures with foreign
compounds , bleaching, or dyeing
Gemstones are
enhanced for a number of reasons:
Beauty: The
treatment of a stone may alter and significantly improve the
appearance of it. The modification may produce a stone that is
cleaner, better color and in some cases more stable than the same
material before treatment.
Price: Fine
natural gem rough is always in short supply and usually very
expensive. If lower quality less costly and more available materials
can be treated or enhanced, the resulting production could look good
and be available at a much lower price..
Demand: The
demand for beautiful gem materials always exceeds the limited supply.
The availability and affordability of enhanced stones fills the void
and makes gemstones accessible to larger segments of the market.
Fashion:
Consumers always seem to want something new. Enhanced or treated
stones can be produced in quantities and in colors which are not
available in natural materials at all.
The most
common treatments for different types of colored stones are: heating
(also known as a "burning"), oiling, irradiation, and diffusion.
Heating —
is a widely accepted enhancement process used on rubies, sapphires,
amber, aquamarine, amethyst, citrine, tanzanite, zircon, topaz, and
tourmaline. This treatment improves the transparency and/or color of
the stones. Techniques range from simply throwing gems in a fire to
be cooked or burned to employing sophisticated electric or gas
furnaces at specific pressures and atmospheric conditions. Much
corundum has been heated to enhance the color. Tourmalines are
frequently heated to lighten the color. Blue zircons are usually
heated and the resulting color is permanent. Since heating is
generally permanent, heated stones do not require special care.
New Heat
Treatment — The new method for producing yellow and orange
sapphires is a natural outgrowth of the traditional heating methods.
Rough sapphire especially from Tanzania, Sri Lanka, and Madagascar is
usually found associated with spinel, zircon, tourmaline, chrysoberyl
and other gemstones. The mine run material is always very difficult
and time consuming to separate before cooking. Thai burners noticed
that some of these other gemstones could actually influence the burn.
More specifically, it was discovered that the introduction of small
quantities of natural chrysoberyl in the crucible would increase the
preponderance of yellow and orange colors in the sapphires being
burned.
Scientists
discovered that beryllium from the chrysoberyl (BeAl2O4) was being
diffused in extremely small and barely measurable quantities and that
this was a critical aspect of the chemical reaction which affected
the coloration in many of the sapphires. Whether beryllium is acting
as a catalyst or not is still the subject of debate. The treatment
can produce complete and total color penetration and is undetectable
by conventional non-destructive gemological testing methods. Although
new laser ablation technologies can detect and measure beryllium and
other trace elements, these determinations are too expensive to be
used for general gemological purposes.
Irradiation
— gems may change color if exposed to radiation. This may come
from radioactive elements within the Earth's crust, or from
artificial sources. Natural radiation may take millions of years to
have an effect, while artificial irradiation may take only few hours
to change a gems’s color. In some cases a gem will revert to
it's original color, or may fade with time. Irradiation is often used
with blue topaz. The stone is irradiated brown and then heated to
produce the blue color. Irradiated stones do not require special care.
Oiling —
is an ancient process used to enhance the clarity of emeralds. Oil is
applied to the emerald and seeps into the fissures, which reach the
stone's surface. Aside from improving clarity, this process may
prevent brittleness. Oiling is generally not permanent and may need
to be reapplied every few years. Special care is required for
cleaning; repairing or mounting oiled stones. This treatment may not
be permanent but it because of its practicality it is generally accepted.
Surface
Diffusion — is another method occasionally used particularly to
produce blue color in sapphires. During treatment, a colorless
sapphire is coated with a titanium and oxide compound and exposed to
heat. This enhances and/or changes the color of the stone and is
quite stable. Because the treatment is only surface related, it is
generally not accepted in the trade.
The term
"unacceptable" applies when the market decides that the
treatment method and its products do not deserve a place in the
market. Most unacceptable treatment methods alter the physical makeup
of the stone in an easily recognizable way. Usually the method is
recognizable due to it's crudity or because the alteration does not
produce a product simulating a naturally occurring gem. Another type
of unacceptable treatment happens when the resulting color is
impermanent. You would not want to buy a vibrantly colored stone
today only to have it lose 90% of its color tomorrow.
Most
treatments that are done to improve the appearance of gemstones do
not change the chemical composition of the stone. Some enhancements
are difficult or impractical to prove definitively.
Beauty
enhancing treatments can produce remarkable results. Less expensive
materials can be transformed into beautiful gemstones. However,
because fine looking enhanced stones are generally much more common
than similar quality untreated stones, their value may be less.
Enhancement should be disclosed. Customers can decide what they want
but they should not be mislead and should be informed of the
existence of any treatments or enhancements when making a purchase.
The information allows them to make their own careful and informed choices.
The following
is a list of accepted gemstone enhancements sanctioned by the
gemstone industry. You may also review FTC abstract guide for the
Definitions and Gemstone Enhancement Codes.
EMERALD:
Usually oiled with colorless oil to improve appearance.
RUBY: Usually
heated to improve color and appearance.
SAPPHIRE:
Usually heated to produce intensity or light color and/or improve
color uniformity.
TANZANITE:
Usually heated to produce violet blue color.
AQUAMARINE:
Usually heated to improve color.
BLUE TOPAZ:
Usually irradiated and heated to produce blue color.
TOURMALINE:
Commonly irradiated to intensify pink, red and purple color.
JADE: Commonly
impregnated with colorless wax.
LAPIS LAZULI:
Commonly impregnated with colorless wax or oil.
CORAL:
Commonly bleached.
PEARLS:
Commonly bleached to improve color and appearance.
BLACK ONYX:
Always dyed. |
