GEMSTONE TREATMENTS

The majority of coloured gemstones undergo some form of treatment to enhance their appearance, durability, or overall quality.
The American Gem Trade Association (AGTA) has established a set of codes to indicate various treatments and enhancements applied to gemstones. These codes help in maintaining transparency and informing you about the processes your gemstones have undergone. Below is a table summarizing these AGTA codes:

 

CODE DESCRIPTION
N

Natural: No modification; natural stones not currently known to be enhanced or have no known modification process.
B

Bleaching: The use of heat, light, and/or other agents to lighten or remove a gemstone’s colour.
C

Coating: Surface enhancements such as lacquering, enameling, inking, foiling, or sputtering of films to improve appearance, provide color, or add special effects.
D

Dyeing: Introduction of coloring matter into a gemstone to give it new color, intensify present color, or improve color uniformity.
F

Filling: Filling of surface-breaking cavities or fissures with colorless glass, plastic, solidified borax, or similar substances to improve durability, appearance, and/or add weight.
H

Heating: Use of heat to effect desired alterations of color, clarity, and/or phenomena. If residue of foreign substances in open fissures is visible under properly illuminated 10X magnification, H and F should be used.
HP

Heating and Pressure: Combined use of heat and pressure to effect desired alterations of color, clarity, and/or phenomena.
I

Impregnation: Impregnation of a porous gemstone with a colorless agent (usually plastic) to improve durability and appearance.
IMIT

Imitation: A simulant, defined as a man-made single crystal product used to simulate the appearance, but not duplicate the characteristic properties, of the natural gemstone it imitates.
L

Lasering: Use of a laser and chemicals to reach and alter inclusions in gemstones, usually diamonds.
O

Oiling/Resin Infusion: 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: Use of neutrons, gamma rays, or beta particles (high-energy electrons) to alter a gemstone’s color, possibly followed by a heating process.
SYN

Synthetic: Materials with essentially the same optical, physical, and chemical properties as their natural counterparts. Stones must be referred to as “synthetic ruby,” “laboratory-grown sapphire,” “lab-created emerald,” etc.
U

Diffusion: Use of chemicals in conjunction with high temperatures to produce artificial color change and/or asterism-producing inclusions.
W

Waxing/Oiling: Impregnation of a colorless wax, paraffin, or oil in porous opaque or translucent gemstones to improve appearance.