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Explanation of Symbols
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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. The following codes have been developed to express any Enhancements that have been done to a gemstone.
S
Y
M
B
O
L
DEFINITION
A
Indicates either a gemstone that is not currently known to be enhanced or one that is so rarely enhanced that to give it an "E" symbol would mislead the public.
Example: Amethyst is rarely known to be treated.
E
Indicates that this gemstone is routinely enhanced.
N
Indicates this particular gemstone has received no enhancement and the seller will guarantee this.
B

Indicates that Bleaching of the gemstone has been done. Bleaching is the use of chemicals or other agents to lighten or remove a gemstone's color.
Example: 'Blonde Tigereye" is enhanced in this manner.
C
Indicates that a Coating has been used as a surface treatments such as waxing, lacquering, enameling, inking, foiling, or sputtering of films to improve appearance, provide color or add special effects.
D
Indicates that Dyeing has occured. Dyeing is the introduction of coloring matter into a gemstone to give it new color, intensify present color or improve color uniformity.
Example: Agate is sometimes enhanced in this manner.
F
Indicates the gemstone has had Filling or Infilling or Stabilizing of some form. This is the filling of surface-breaking cavities or porous gem material with colored or colorless glass, plastic or other hardened material to improve appearance, durability, and/or weight.
Example: Turquoise is commonly enhanced in this manner.
G
Indicates the gemstone has undergone some form of Gamma or Electron Irradiation. This is the use of gamma and/or electron bombardment to alter a gemstone's color. May be followed by a heating process ("H").
Example: Blue Topaz is commonly enhanced in this manner.
H
Indicates the stone has been heated to effect desired alteration of color, clarity, and/or phenomena.
Example: Sapphire is commonly enhanced in this manner.
Example: Citrine is commonly enhanced in this manner.
L
Indicates the gemstone has undergone the use of a laser and chemicals to reach and alter inclusion.
Example: Diamond is sometimes enhanced in this manner.
O
Indicates the introduction of a colorless oil, wax, natural resin, or unhardened man-made materials into fissured or porous gemstones was made to improve appearance.
Example: Commercial grade Emerald is commonly enhanced in this manner
.
R
Indicates the gemstone has undergone Irradiation. This is the use of neutron or a combination of neutron with any other bombardment to alter a gemstone's color. May be followed by a heating process ("H").
Example: Blue Topaz is commonly enhanced in this manner.
U
Indicates the gemstone has undergone Diffusion which is the use of chemicals in conjunction with high temperatures to produce a relatively shallow subsurface layer of color and/or asterism-producing inclusions.
Example: Difusion treated Sapphire is enhanced in this manner.

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