The application of heat to enhance the color and/or clarity of gemstones has been a common practice around the globe for centuries. It is part of the standard polishing and finishing process for many colored gemstones. As such, it is accepted by the jewelry industry and the American Gem Trade Association. The enhanced color and/or clarity of heat-treated gemstones is permanent.
Infusion
The filling of a gem material with an oil, wax, glass, resin or other material, colored or colorless, to improve appearance. This process began centuries ago by gemstone merchants who found that immersing emeralds in oil or waxes made them look clearer to the unaided eye. This practice continues today with many colored gemstones.
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The use of wax, resin or oil applied to the exterior of a porous colored gemstone to protect the natural substance, and to improve sturdiness and appearance.
Bleaching
The application of chemicals or other elements to lighten or enhance color consistency.
Dyeing
The act of adding coloring agents so that they permeate a colored gemstone to enhance or alter color.