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