Feature Gems & Gemology, Winter 1982, Vol. 18, No. 4

Gem-Quality Grossular Garnets

The gemological classification and identification of gem grossular garnets is examined through the study of 105 gem-quality grossulars. These specimens were measured for refractive index, specific gravity, absorption spectrum, color, and chemical composition. From these data, the authors were able to reexamine the ranges of physical and optical properties that are characteristic of the gem species grossular. In addition, they discuss the problems encountered in defining the two gem varieties of grossular, tsavorite and hessonite.