Gemstone Enhancement Codes
Published by the American Gem Trade Association
Enhancement: Any treatment process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, or availability of a gemstone.
The "N" symbol appears on the chart only for natural stones which are not currently known to be enhanced; however, the "N" symbol can also be used for other natural gemstones in the event that a gemstone has received no enhancement and the seller will provide a guarantee that there has been none.
The "E" symbol indicates that a gemstone has undergone its traditional enhancement process.
The use of heat, light and/or other agents to lighten or remove a gemstone's color.
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.
The introduction of coloring matter into a gemstone to give it new color, intensify present color or improve color uniformity.
The filling of surface-breaking cavities or fissures with colorless glass, plastic, solidified borax or similar substances. This process may improve durability, appearance, and/or add weight.
The use of heat to effect desired alteration of color, clarity, and/or phenomena (if residue of foreign substances in open fractures is visible under properly illuminated 10X magnification HF should be used.
The use of heat and pressure combined to effect desired alterations of color clarity and/or phenomena.
The impregnation of a porous gemstone with a colorless agent (usually plastic) to improve durability and appearance.
The use of a laser and chemicals to reach and alter inclusions in diamonds.
The filling of surface-breaking fissures with colorless oil, wax, resin, or other colorless substances, except glass or plastic, to improve the gemstones appearance.
The use of neutrons, gamma rays or beta particles (high energy electrons) to alter a gemstones color. The irradiation may be followed by a heating process.
The use of chemicals in conjunction with high temperatures to produce artificial color and/or asterism-producing inclusions.
The impregnation of a colorless wax, paraffin, and oil in porous opaque or translucent gemstones to improve appearance.
All enhancement codes are standardized by the American Gem Trade Association