Stibiotantalite: Gemstones Information
Stibiotantalite is Sb(Ta,Nb)O4 and forms semi-transparent yellowish to brownish equant or flattened prismatic crystals of the orthorhombic system with hardness 5.5 and SG 7.3. The RI for the alpha, beta and gamma rays is 2.374, 2.404, 2.457, biaxial positive with birefringence 0.90. Some specimens may show a faint RE absorption spectrum.Stibiotantalite occurs in complex granite pegmatites. Uncommon facetable material is most likely to have come from the Muiane and other mines, Alto Ligonha, Mozambique, or from the Himalaya mine, Mesa Grande district, SanDiego County, California.