Columbite, also called niobite, niobite-tantalite and columbate [(Fe, Mn)(Nb, Ta)2O6], is a black mineral group that's an ore of niobium and tantalum. It has a submetallic luster and a high specific gravity and is a niobate of iron and manganese, containing tantalate of iron. This mineral group was first found at Haddam, Middlesex County, Connecticut, in New England, USA. It forms a series with the tantalum-dominant analogue ferrotantalite and one with the manganese-dominant analogue manganocol… (More on Columbite)