Specific Enhancement Codes :

B: Bleaching - Use of chemicals to lighten or remove a gem's color
C: Coating - Use of surface treatments such as films, lacquers, etc. to provide color or other special effects
D: Dyeing - The introduction of coloring matter into a gem to give it a new color or greater intensity
F: Filling - Incorporation of colorless borax or other substances into cracks as a by-product of heating the stone, used only if such material is visible at 10x.
G: Gamma/Electron Radiation - The use of gamma or electron irradiation for the purpose of changing a gem's color, may be followed by a heating process to stabilize the color. Such stones do not exhibit residual radioactivity.
H: Heating - The use of heat to clarify, change color or create phenomena in gems. Any filler materials, which enter the gem, as a result must not be visible in fractures at 10x.
I: Infilling - The intentional filling of surface breaking cracks and cavities with a foreign material such as synthetic resins with hardeners (Opticon), glass or plastic.
L: Lasering - The use of a laser to drill into a stone and remove or alter an inclusion, refers specifically to diamonds
O: Oiling or Resin Infusion - The intentional filling of surface breaking cavities and cracks in transparent or translucent gems with a colorless oil, wax, resin or man-made unhardened resin.
R: Irradiation - The use of neutron bombardment to alter color. This process creates residual radioactivity and such stones must receive a Nuclear Regulatory Commission safety release prior to sale. Usually used in combination with other radiation and or heating treatments.
S: Bonding - The intentional use of a colorless bonding agent (usually plastic) within a porous gemstone.
D: Diffusion - The use of specific chemicals during a high temperature heating process for the purpose of penetrating the surface layer (usually to a slight depth only) with coloring or star-making chemicals. Such treatment is not generally accepted and stones sold with this enhancement must be specifically labeled as diffused.
W: Waxing/Oiling - The impregnation of colorless wax, oil or paraffin into porous opaque gems to improve appearance.