Symbols for Specific forms of Enhancement

B Bleaching
The use of heat, light, and/or other agents to lighten or remove a gemstone’s color

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.

D Dyeing
The introduction of coloring matter into a gemstone to give it new color, intensify present color or improve color uniformity.

F Filling
The filling of surface-breaking cavities or fissures with colorless glass, plastic, solidified borax or similar substances, which are visible under properly illuminated 10X magnification. The process will improve durability, appearance, and/or add weight.

H Heating
The use of heat to effect desired alteration of color, clarity, and/or phenomena (Residue of foreign substances in open fractures is not visible under properly illuminated 10X magnification).

HP Heat & Pressure
The use of heat and pressure combined to effect 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.

L Lasering
The use of a laser and chemicals to reach and alter inclusions in diamonds.

O Oiling/Resin Infusion
The filling of surface-breaking fissures with colorless oil, wax, resin, or other colorless substances, except glass or plastic, to improve the gemstone’s appearance.

R Radiation
The use of neutrons requiring an environmental safety release from the Nuclear Regulatory Commission (NRC), Gamma and/or electron bombardment to alter a gemstone’s color. The irradiation may be followed by a heating process.

U Diffusion
The use of chemicals in conjunction with high temperatures to produce color and/or asterism-producing inclusions.

W Waxing/Oiling
The impregnation of colorless wax, paraffin, and oil in porous opaque or translucent gemstones to improve appearance.