Columbite is a natural oxide of niobium, tantalum, ferrous iron, and manganese. Some tin and tungsten may be present in the mineral. Columbium, in the form of ferrocolumbium, is used mostly as an additive in steel making and in superalloys for such applications as heat-resisting and combustion equipment, jet engine components, and rocket subassemblies, in cemented carbides, and in superconductors. Brazil and Canada are the world’s leading producers.