Over 99% of gems sold have undergone some kind of enhancement. Here is a list of the most common ones:

ASBL Assembled

“ASBL” is the code for products made for multiple layers or combinations of manufactured and/or natural material joined together to increase stabilty and/or imitate the appearance of a natural gemstone, create a unique design or generate unusual color combinations.


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


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.


The introduction of coloring matter inside 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.

Heat & Pressure

The use of heat and pressure combined to effect desired alterations of color, clarity and/or phemonena.

IMIT Imitation

“IMIT” is the code used for a manufactured product fabricated in such materials as glass, ceramic or plastic designed to imitate or resemble the appearance, but not duplicate the characteristic properties of a natural gemstone.

“IMIT” is also the 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.


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 gemstones, usually diamonds.

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.


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.


Synthetic materials have essentially the same optical, physical and chemical properties as a naturally occurring counterpart.


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 transluscent gemstones to improve appearance.