Ferrocolumbite

Ferrocolumbite, also called niobite, niobite-tantalite, columbate and columbite [(Fe, Mn)(Nb, Ta)₂O₆] is a black mineral that is 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 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 Manganocolumbite.