Columbite, also called niobite, niobite-tantalite and columbate , Mn 2O 6], is a black mineral. It has a submetallic luster and a high density and is a niobate of iron. This mineral group was first found in Haddam, Connecticut , in the United States. It forms a series with the tantalum -dominant analogue ferrotantalite and one with the manganese-dominant analogue manganocolumbite. The iron-rich member of the columbite group is ferrocolumbite. Some tin and tungsten may be present in the mineral. Yttrocolumbite is the yttrium-rich columbite with the formula (Y,U,Fe)(Nb,Ta)O 4. It is a radioactive mineral found in Mozambique.
Columbite has the same composition and crystal symmetry (orthorhombic. In fact, the two are often grouped together as a semi-singular mineral series called columbite-tantalite or coltan in many mineral guides. However, tantalite has a much greater specific gravity than columbite, more than 8.0 compared to columbite's 5.2.
Columbite is also very similar to tapiolite. Those minerals have same chemical composition but different crystal symmetry: orthorhombic for columbite and tetragonal The largest documented single crystal of columbite consisted of plates 6 mm (0.24 in) thick measuring 76 cm × 61 cm (30 in × 24 in).