|Color||Black, brownish black.|
|Crystal habit||Massive - Granular - Common texture observed in granite and other igneous rock; Striated - Parallel lines on crystal surface or cleavage face.|
|Crystal system||Orthorhombic, (2/m 2/m 2/m), SpaceGroup = Pcan|
|Fracture||Sub Conchoidal - Fractures developed in brittle materials characterized by semi-curving surfaces.|
|Mohs scale hardness||6|
|Specific gravity||5.3 - 7.3, Average = 6.3|
|Optical properties||Biaxial (+), b=2.29-2.4|
|Other characteristics||non-radioactive, non-fluorescent.|
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 (orthorombic) 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.
Columbite is also very similar to tapiolite. Those minerals have same chemical composition but different crystal symmetry: orthorhombic for columbite and tetragonal for tapiolite. The largest documented single crystal of columbite consisted of plates 6 millimetres (0.24 in) thick measuring 76 by 61 centimetres (30 in × 24 in).
The occurrence of columbite in the United States was made known from a specimen sent by Governor John Winthrop of Connecticut to Hans Sloane, President of the Royal Society of Great Britain. It was in columbite that Charles Hatchett discovered, in 1801, the element niobium, which he himself called columbium, after Columbia, a name for the United States, whence came the specimen in the British Museum collection which he examined.
- Columbite-(Fe) Mineral Data
- Columbite-(Fe) on Mindat.org
- mindat.org Tantalite
- P. Cerny et al. "The tantalite-tapiolite gap: natural assemblages versus experimental data" Canadian Mineralogist 30 (1992) 587 free download
- P. C. Rickwood (1981). "The largest crystals". American Mineralogist 66: 885–907.
- "Columbite". New International Encyclopedia. 1905.
- Chisholm, Hugh, ed. (1911). "Columbite". Encyclopædia Britannica (11th ed.). Cambridge University Press.
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