Gem Treatments and Enhancements

Improving gem appearance and quality through treatments increases the supply of commercially important gems.
Disclosure of all treatments, including suspected or probable ones, is essential for building trust in the industry.

Gems commonly subjected to heat treatment include corundum, tanzanite, zircon, topaz, aquamarine, and amber.
Heat treatment changes the way gems absorb light, altering their color, by affecting the gain or loss of electrons in trace elements.
Heat treatment can alter corundum color and create or eliminate phenomena and inclusions.
Low-temperature heating can improve the appearance of ruby and pink sapphire by removing blue color zones.
Producing blue color in geuda sapphire requires high-temperature heating in a reducing environment, followed by rapid cooling.

Lattice diffusion with heavier elements like titanium and chromium produces a shallow layer of color that might be removed by minor repolishing.
A combination of beryllium diffusion and heat treatment can improve color in some dark blue sapphires and make them more marketable.
The color resulting from lattice diffusion with beryllium can penetrate the entire stone.

Fracture filling is the most common form of clarity enhancement.
Almost all emeralds on the market are subjected to clarity enhancement.
Filling with glass or resin can stabilize highly fractured, otherwise unusable rough, making it suitable for jewelry use.

Irradiated color is not always stable and can be destroyed by heat or light exposure.
Commonly irradiated gems include topaz, tourmaline, and cultured pearl.
Bleaching is a fairly common pearl treatment, and jadeite is often treated with a combination of bleaching and impregnation.
Dyeing is one of the oldest gem treatments, commonly used for cultured pearl, lapis lazuli, chalcedony, and coral.

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