American Gem Trade Association Codes
Enhancement: Any treatment process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, or availability of a gemstone.
N: 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.
E: The “E” symbol indicates that a gemstone has undergone its traditional enhancement process.
| ASBL Assembled: “ASBL” is the tag code for products made for multiple layers or combinations of manufactured and/or natural material fused, bonded or otherwise joined together to increase stabilty and/or imitate the appearance of a natural gemstone, create a unique design or generate unusual color combinations. |
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 laquering, 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. This process may improve durability, appearance, and/or add weight. |
H Heating: 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. |
| HP Heat & Pressure: The use of heat and pressure combined to effect desired alterations of color clarity and/or phemonena. |
IMIT Imitation: “IMIT” is also the tag code for a simulant, which is defined as a man-made single crystal product that is used to simulate appearance, but not duplicate the characteristic properties of a natural gemstone it imitates. |
I Impregnation: The impregnation of a porous gemstone with a colorless agent (usually plastic) to improve durability and appearance. |
| L
Lasering: The use of a laser and chemicals to reach and alter inclusions in gemstones, unusally 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
Irradiation: The use of neutrons, gamma rays or beta particles (high energy electrons) to alter a gemstone’s color. The irradiation may be followed by a heating process. |
| SYN Synthetic: The tag code may be used to describe “synthetic” materials that have essentially the same optical, physical and chemical properties as a naturally occurring counterpart. |
U Diffusion: The use of chemicals in conjunction with high temperatures to produce artificial color and/or asterism-producing inclusions. |
W Waxing/Oiling: The impregnation of a colorless wax, paraffin, and oil in porous opaque or transluscent gemstones to improve appearance. |
Information from AGTA Standard Gemstone Treatments
