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Fall 1992, Volume 28, Issue 3

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Unstable Radiation-Induced Yellow-Green Color in Grossular Garnet
Kurt Nassau, George R. Rossman, and Darwin L. Wood


Although conventional wisdom has been that irradiation will not alter the color of garnets, exposure of some colorless to pale-hued African grossulars to either 60Cr or 137Cs gamma rays turns them light yellow-green. The resulting color is unstable and fades within hours to days in sunlight, and within weeks in the dark. The spectra of the radiation-enhanced garnets differ from those of similar-appearing naturally colored grossulars. In the dark, the irradiation-related absorption features undergo two stages of fading: an initial period of relatively rapid fading, followed by a longer period of slow fading. In daylight, a single rate of even faster fading is observed.

Appears on pages 188-191

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