Chemical Formula: (Fe,Mn)(Nb,Ta)2O6
Locality: Globe and Harding pegmatites, Taos County, New Mexico, USA.
Name Origin: Named for the MANGANese content and the relationship to columbite (ferrocolumbite).
Columbite, also called niobite, niobite-tantalite and columbate [(Fe, Mn)Nb2O6], is a black mineral group that is an ore of niobium. It has a submetallic luster and a high density and is a niobate of iron and manganese. 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)O4. It is a radioactive mineral found in Mozambique.
Columbite has the same composition and crystal symmetry (orthorhombic) as tantalite. 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.
Physical Properties of Columbite-(Mn)
Cleavage: {010} Distinct, {100} Indistinct
Color: Brownish black, Black.
Density: 5.28
Diaphaneity: Opaque
Fracture: Brittle – Subconchoidal – Brittle frature with subconchoidal fragments
Hardness: 6 – Orthoclase
Luster: Sub Metallic
Streak: reddish black
Photos
(Nb,Ta)2O6 Locality: Globe and Harding pegmatites, Taos County, New Mexico, USA. Name Origin: Named for the MANGANese){kind=link}