Feature Gems & Gemology, Winter 1984, Vol. 20, No. 4

Pyrope-Spessartine Garnets with Unusual Color Behavior

The study of garnets by GIA’s Department of Research continues with a collection of 32 garnets that display a variety of hues and yet share a common tendency to show different colors under different sources of light. Even when very slight, the change of color is invariably greater than that encountered in other types of garnets. These unusual garnets proved to be composed principally of a variable mixture of pyrope (25-60 wt. %) and spessartine (20-56 wt. %) with considerable almandine (2-17 wt. %) and grossular (3-23 wt. %) also present. Their primary chemical distinction lies in their V2O3+Cr2O3 content, which is always in excess of 0.2 wt. %. In conjunction with their distinctive color behavior, these garnets may also be characterized on the basis of specific gravity and absorption spectrum.