White; symbol, BN; hexagonal rhombohedral, crystals or powder; the powder has a Mohs hardness of 2; sublimes at about 3,000 degrees C; anisotropic; some properties vary according to the method of preparation and the crystal form. Used as a refractory; a high-temperature lubricant, as in glass molds; in furnace insulation; and in molten-metal pump parts.