boehmite

boehmite, white and relatively soft basic aluminum oxide [AlO(OH)] that is a common mineral in bauxite, in which it forms disseminated grains or pealike masses. It is especially abundant in European bauxites, sometimes as the main constituent; bauxites from the Western Hemisphere commonly contain only a few percent boehmite. Deposits exist at Gánt and Baratka, Hung.; Stangenrode, Ger.; Ayr, Scot.; and Recoux, Péreille, and Cadarcet, France. Boehmite is dimorphous (identical in composition but differing in crystal structure) with diaspore; its crystals have orthorhombic symmetry. For detailed physical properties, see oxide mineral (table).