Taaffeite: Gemstones Information
Recent authorities, including Fleischer’s Glossary of Mineral Species 2004 now use the name magnesio-taaffeite but for the purpose of this listing I have retained the original name. Taaffeite is Mg3Al8BeO16 and forms mauve or lilac, red to brown transparent to translucent hexagonal crystals of the hexagonal system with hardness 8–8.5 and SG 3.605–3.613. Unusually the type species is a faceted stone, originally believed to be spinel. The RI for the ordinary and extraordinary rays is 1.721–1.726 and 1.717–1.727, uniaxial negative (may be anom- alously biaxial). The birefringence is 0.004–0.009. Taaffeite occurs in gem gravels or in skarns at the contact between dolostones and lime stones with beryllium-bearing granite. The productive gem gravels are located in Sri Lanka; an in situ occurrence in China is located on Hsianghualing Ridge, China. Taaffeite has also been found 6 km west of Mt Painter, Southern Australia. Recently, a purplish brown chatoy ant taaffeite has been found in Sri Lanka, the eye arising from parallel reflective planar inclusions with striations.