Gemstone Enhancement Codes (based on AGTA
guidelines)
B=Bleaching
The use of heat, light and/or chemicals or other
agents to lighten or remove a gemstone's color. This is often
accompanied by subsequent dying and/or impregnation. Example:
bleached cultured pearl; bleached/impregnated jadeite
('B-jade)
C=Coating
The use of such surface enhancements as lacquering, enameling,
inking, foiling, or sputtering of films to improve appearance,
provide color or add other special effects. Example: coated
diamond, coated topaz
D=Dyeing (Staining)
The introduction of coloring matter into a gemstone to give
it new color, intensify existing color or improve color uniformity.
Example: dyed green jadeite
E=Normally Enhanced
The "E" symbol is used for gemstones that are
routinely enhanced. Since many enhancements are difficult or
impractical to prove definitively, unless otherwise indicated, our
approach is to assume that such enhancements have been applied to
that particular gemstone. This assumption is made to protect both
buyer and seller. If a more specific method of enhancement is
known, then the specific enhancement code will be used.
F=Filling
The filling of surface-breaking cavities or fissures with
colorless glass, plastic, or some similar substance. This process
will improve durability, appearance and/or weight. Example:
ruby
Fh=Flux healing
During heat enhancement, fluxes (or heat alone) may be used to heal
fractures/fissures which were formerly open. The process dissolves
the walls of the fractures and redeposits the molten gem material,
healing the fractures closed. Example: ruby (particularly that from
Mong Hsu, Burma)
H=Heating
The use of heat to alter color, clarity, and/or phenomena. Example:
Ruby, sapphire, tanzanite, aquamarine, demantoid garnet
HP=Heating & Pressure
The use of heat and pressure combined to affect
desired alterations of color and/or clarity.
I=Impregnation
The impregnation of a porous gemstone with a
colorless agent (usually plastic) to give it durability and improve
appearance. Example: Stabilized turquoise.
L=Lasering
The use of a laser and chemicals to reach and alter
inclusions. Example: diamond
N=Not Enhanced
The "N" symbol is used on our invoices to indicate
one of two situations. First, there are certain gemstones that are
not currently known to be enhanced (alexandrite, some garnets,
etc.) Second the "N" symbol may also be used for a gem where it can
be proved via gemological or other means that a gem has not been
subjected to any enhancement. When you see the "N" symbol on our
invoice, we guarantee that the gem in question is
unenhanced.
O=Oiling/Resin Infusion
The filling of surface-breaking fissures with a
colorless oil, wax, resin or other colorless substances, except
glass or plastic, to improve the gemstone's appearance. Example:
emerald
R=Irradiation
The use of neutrons, gamma, ultraviolet and/or
electron bombardment to alter a gemstone's color. The irradiation
may be followed by a heating process. Example: Blue topaz, colored
diamonds
U=Lattice ('bulk' or 'surface')
Diffusion
Outside-in diffusion of coloring chemicals via
high-temperature heat treatment to produce color and/or asterism.
Example: lattice diffusion-treated sapphire
W=Waxing/Oiling
The impregnation of a colorless wax; paraffin
and/or oil in porous gemstones to improve appearance. Example:
jadeite
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Enhancement Information
