Columbite

Columbite, dense oxide mineral composed of manganese, niobium, and iron, general chemical formula (Fe,Mn)Nb₂O₆. The element tantalum sometimes wholly or partially replaces niobium. When the mineral contains more tantalum than niobium, it is called tantalite. Both are black, often iridescent, and are found in granite rocks called pegmatites.

See also: Niobium; Tantalum.