Columbite: a mineral belonging to the Oxide Class. It crystallizes in the Orthorhombic System, bipyramidal class. It occurs as short prismatic or tabular crystals, or as compact aggregates. Contact twins are common. The crystals are black with a metallic appearance and often show iridescent tarnish. Columbite is a complex mixture of Niobite and Tantalite, with pure end-members being very rare. It is very hard, very dense, brittle, and easily cleavable. Columbite is an essential ore for the extraction of Niobium and Tantalum, which are used in metallurgy for high-melting alloys, corrosion-resistant materials (stainless steel), and electromagnetic superconductors.
