Sellaite: Gemstones Information

Sellaite is MgF2 and occurs as short prismatic colourless or white transparent crystals of the tetragonal system with perfect cleavage in two directions, hardness 5–5.5 and SG 3.15. The RI for the ordinary and extraordinary ray is 1.378 and 1.390, uniaxial positive, birefringence 0.012. Facetable crystals occur in a metamorphic magnesite deposit at the Brumado mine, Bahia, Brazil.