'Cobalt-Blue' Gem Spinels
Similarities between natural spinels - with intense blue colour - and synthetic material, have led to difficulties in the recognition of the natural stones by traditional methods.
Gemstones of Pakistan: Emerald, Ruby and Spinel
This article reports on three gem materials currently being mined in Pakistan.
Sri Lanka: The Gem Island
An overview of the many types of gem-quality material, and its inclusions, currently found in Sri Lanka.