Treatment refers to any process other than cutting and polishing that improves the appearance of the color or clarity, or that are used to alter the appearance (color, clarity or phenomena), durability, value, or supply of a gemstone. Today, most gems are treated to improve appearance. Treatment processes can consist of heat, irradiation, dyeing, oiling, or other processes. Detection of these treatments may be easy to nearly impossible. Treatments should always be disclosed to the consumer. The following is adapted from the American Gem Trade Association Treatment Disclosure Codes.
Clarity enhancement/Fracture filling
Clarity enhancement/Fracture filling refers to the filling of surface breaking cavities or fissures with a colorless glass, plastic or similar substance. This process is done to improve durability, color and transparency and may add weight.
Dyeing refers to one of the oldest treatments recorded. The treatment involves the introduction of a coloring agent into a gemstone to give it a new color, intensify an existing color or improve color uniformity.
This process is a form of heat treatment that is typically encountered with ruby. During heat treatment fluxes, or in some instances heat alone, is used to induce the healing of fractures by partial melting and controlled cooling of the stone during which a nutrient rich solution develops in the fractures and crystallizes as the stone cools, thus healing the fracture.
The heat treatment of gems is the most common treatment technique used on gems. Reference to heat treatment of gems is found in gemological literature dating back more than one thousand years. However, widespread use dates back only about fifty years. Unlike most gem treatments, heat treatment is not detectable in most gem varieties including aquamarine, citrine and tanzanite. This treatment is usually detectable in ruby and sapphire. Heat treated gems are stable and the treatment is usually permanent. The vast majority of gemstones are heated to alter their color. In ruby and sapphire the treatment is often performed to improve color and clarity. The alteration usually involves burning out secondary colors present in an attempt to improve the appearance.
Irradiation refers to the use of neutrons, gamma, ultraviolet and/or electron bombardment to alter a gemstone’s color. The irradiation stage of the process is then usually followed by a heating phase to effect the change. Blue topaz is typically produced by irradiation.
Oiling refers to a filling of surface reaching cracks or fissures in a gem with a colorless oil or resin, wax or other substance except glass or plastic, to improve the gemstone’s appearance. The purpose is to diminish the visibly of fractures and thus improve transparency in the stone. The treatment is usually not permanent.
This is a brief list of treatments commonly encountered in the gem trade. It is not all inclusive. Other treatments exist.