Irrradiation of Colored Gemstones

George R. Rossman
 Division of Geological and Planetary Sciences
California Institute of Technoogy
Pasadena, CA  91125


Natural radiation produces color in a variety of gem materials. Laboratory irradiation techniques are capable of both enhancing these colors in some stones and developing them when they did not exist in the rough gem material. Laboratory irradiation can also produce colors which are unstable in nature or which have no known natural counterpart. Often, the colors induced by natural radiation are undesirable and must be removed by heat treatment such as in the case of zircon or green aquamarine. Other colors formed by natural radiation are removed by exposure to light. Laboratory studies are aimed at understanding the details of the radiation induced changes. Oxidation state changes in minor components are associated with the irradiation colors of beryl, kunzite, and tourmaline. Minor amounts of aluminum and iron in quartz control its response to radiation. The origin of the blue irradiation color of topaz has yet to be determined.

last updated: 3-Sep-2017