The Probert Encyclopaedia of Rocks & Minerals

COLUMBITE

Columbite is a mineral of a black colour, sub-metallic lustre, and high specific gravity. It is a niobate (or columbate) of iron and manganese, containing tantalate of iron, was first found in New England and is the main ore of niobium and tantalum. It shows a bluish iridescent fracture surface and is used in metallurgy to create heat-resistant alloys and in the rust proofing of stainless steel. It has the formulae (Fe,Mn)(Nb, Ta)2O6 and a relative hardness of 6.
Research Columbite