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The Mineral columbite

Large Stubby Black Columbite Crystal

Columbite forms a solid solution series with Tantalite known as the Columbite-Tantalite series. Columbite is the niobium-rich member, and Tantalite is the tantalum-rich member. Columbite is named after its niobium content, which was previous known as columbium prior to its renaming. Columbite is the most important mineral containing the rare element niobium and is its main ore.

The name Columbite has been discredited by the IMA, with the more specific designations of Columbite-(Fe) (also known as Ferrocolumbite), and Columbite-(Mn) (also known as Manganocolumbite) being used for this mineral's IMA-accepted nomenclature. Most Columbite specimens are of the Ferrocolumbite; Manganocolumbite is far less common. An even rarer member of this series is (Columbite-(Mg) (Magnesiocolumbite), a magnesium-rich member. In general, despite being discredited, the name Columbite is still used without further designation, and often it is simply labelled as Columbite-Tantalite, since the exact species can be difficult to determine.

Chemical Formula

Ferrocolumbite: (Fe,Mn)(Nb,Ta)₂O₆

Manganocolumbite: (Mn,Fe)(Nb,Ta)₂O₆

Magnesiocolumbite: (Mg,Mn,Fe)(Nb,Ta)₂O₆

Color

Dark gray to black, also brownish-black. May have blue iridescence upon fresh fracture surfaces. Sometimes oxidizes with a yellowish coating.

Crystal System

Orthorhombic

Properties

Streak
Dark red, dark brown, black

Hardness
6

Transparency
Opaque

Specific Gravity
5.3 - 6.5

Luster
Submetallic, greasy, dull

Cleavage
1,1

Fracture
Conchoidal, uneven

Tenacity
Brittle

Other ID Marks
May exhibit weak attraction to magnetic fields.

Crystal Habits

In prismatic crystals, often with a somewhat flattened appearance. Tabular or equant habits are less common. Crystals may be striated or have growth patterns, and sometimes have complex terminations including uneven tapering habits and pyramidal. Crystals are often crudely formed and may have undefined faces. Also bladed, grainy, and massive.

3D Crystal Atlas

Additional Information

Composition
Oxide of iron, manganese, niobium, and tantalum. One series member contains a dominance of magnesium.

In Group
Oxides; Multiple Oxides

Striking Features
Crystal habit, mode of occurrence, and high specific gravity.

Environment
In granite pegmatites, as well as alluvial deposits containing weathered pegmatite fragments.

Rock Type
Igneous

Other Names

Niobite

Uses

Columbite is as an ore of the rare elements niobium and tantalum.

Noteworthy Localities

Columbite occurs in many of the important pegmatite districts worldwide. It has been found in many locations in Minas Gerais, Brazil, especially at Araçuaí; Governador Valadares; and São José da Safira. Other important worldwide locations include the Tsaramanga pegmatite, Betafo District, Antananarivo Province, Madagascar; and Iveland, Aust-Agder, Norway.

In the U.S., many of the old pegmatite quarries have produced some of the best forms of this mineral. Specific localities include Bethel, Fairfield Co.; Haddam and Portland, Middlesex Co.; South Glastonbury, Hartford Co.; and Woodbury, Litchfield Co. Other U.S. localities include the Ham and Weeks Mine, Wakefield, Carroll Co., New Hampshire; Bedford, Westchester Co., New York; the Rutherford Mine, Amelia, Amelia Co., Virginia; and Spruce Pine, Mitchell Co., North Carolina.