Specific Forms of Enhancement.

Bleaching:  The use of chemicals or other agents to lighten or remove a gemstone’s color.

Coating:  The use of such methods as lacquering, enameling, inking, foiling, or sputtering of films to improve appearance, provide color or add other special effects.

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

Filling:  The masking of surface cavities or fractures usually with glass of plastic, or another foreign substance to improve appearance,

Heating:  The use of heat to effect desired alteration of color and/or clarity.

Impregnation:  General infusion of a substance such as paraffin or wax into a porous material.

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

Oiling:  The penetration of colorless oil into voids and faults to improve overall appearance.

Stabilization:  The use of a colorless bonding agent (commonly plastic) within a gemstone to improve durability and appearance.