Feature Gems & Gemology, Fall 1989, Vol. 25, No. 3

Thermal Alteration of Inclusions in "Rutilated" Topaz

Faceted colorless topaz containing acicular inclusions has been offered for sale as "rutilated" topaz. Earlier investigations have shown the inclusions to be limonite-stained etched dislocation channels. This article reports on the use of heat treatment to alter the limonite staining to hematite, thus changing the color of the inclusions and making them more prominent.