Sphene: Gemstones Information
Sphene is CaTiSiO5. The name titanite is universally used by mineralogists today. It forms characteristically wedge-shaped crystals of the monoclinic system; cleavage is good rather than perfect but crystals may show parting due to twinning. Colours may be pale yellow to brown, green or, rarely, emerald green. The hardness is 5–5.5 and the SG 3.45–3.55. Sphene has a near adamantine lustre and a notably high dispersion, 0.051. The RI for the alpha, beta and gamma rays is 1.843–1.950, 1.870–2.034, 1.943–2.110, biaxial positive with birefringence 0.100–0.192. Some degree of metamictization may be present. Some specimens may show faint RE absorption lines. Sphene occurs as a common accessory mineral in igneous rocks, also in schists and gneisses. Fine crystals are found in Baja California, Mexico, at El Rodeo,La Huerta and in particular at Pino Solo where emerald-green crystals coloured by Cr have been found. Sphene also provides fine crystals at several locations in Switzerland, including Tavetsch, Graubunden and sites in Valais and Ticino cantons. Transparent orange sphene has been found in Myanmar. Emerald-green specimens have been found in the Urals, Russia.