gems, spinel, Tanzania, spinel inclusions

A brief gemological report on spinels from Tanzania’s Umba Valley, occurring in pink, red, orangish red and bluish violet colors. The specimens examined had refractive indices of 1.713–1.718 and specific gravities of 3.54–3.69. Spectroscopic examination was used to investigate the causes of the different colors. The note documents the range of gem spinel then reaching the market from the Umba Valley and provides basic properties useful for characterizing this East African material.