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Guide to Gemstone Enhancements

This guide provides information on the most common enhancement and treatment processes for some of the most popular gemstones.


Laser drilling is commonly used in the clarity enhancement of diamonds. A focused laser beam is used to drill a narrow channel from the surface to dark inclusions which may then be acid bleached.

Fracture filling treatment is done occasionally to improve the apparent clarity of diamonds. Surface-reaching breaks are filled with a trans?parent substance.

Artificial irradiation of diamonds has attained some importance due to the coloring effect produced when the stone is bombarded with particles of atomic size. Irradiation produces a green color which can be further altered to fancy yellow brown, orange, and rare pink by subsequent heating under controlled conditions.

Ruby & Sapphire

Heat treatment is widely used as a means to produce intense blue hues in sapphires and bright red hues in rubies. High temperature treatment of rubies and sapphires may cause a star effect, or lighten dark blue hues of sapphires.

Cavity filling is a common treatment in which a glass-like substance is applied to seal surface pits and cavities, add weight and improve the appearance of rubies and some sapphires.


Oiling and infilling are very widespread practices. Surface reaching breaks in emeralds are filled with various materials to improve appearance.

Traditionally, oiling has been performed with organic substances such as cedarwood oil, balsam, wax, and palm oil. In recent years, new commercial techniques for infilling surface breaks have been developed to improve clarity and add weight. Materials used in these procedures include glass, epoxy plastic, and other artificial substances.


Heat treatment of green-blue aquamarine is routinely done to produce beautiful sky-blue hues.


Heat treatment of amethyst produces most citrine.


Impregnation with colorless oil, wax, or plastic is sometimes used to improve the play of color and hide the cracks of poor quality white opal.

Sugar treatment and smoke treatment may be used to deepen the background color and intensify the play of color of black opal.


Heat treatment of tanzanite produces violet and deep blue colors. Most tanzanite is heat treated.


Heat treatment is responsible for producing pink topaz from yellow, orange, and brown topaz stones which contain chromium.

Irradiation and subsequent heating produce the well known blue color. Most blue topaz on the market has been treated.


Irradiation is common and produces deep pink tourmaline from very light pink stones.

Heat treatment can lighten very dark blue-green stones and produce blue hues by heating purple and brown specimens.