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Dominant species
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Manganocolumbite
Manganocolumbite
Chemical
Formula
Fe2+Nb2O6
Species
Oxides & Hydroxides
Crystal
System
Orthorhombic
Mohs
Scale
6
Specific
Gravity
5.3-7.3
Color
Black, brownish black.
Streak
blackish brown
Luster
sub-metallic
Cleavage
Distinct
Fracture
Sub Conchoidal - Fractures developed in brittle materials characterized by semi-curving surfaces.
Crystal Habit:Massive - Granular - Common texture observed in granite and other igneous rock; Striated - Parallel lines on crystal surface or cleavage face.
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, USA. 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 × 24 in).


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