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(Fe,Mn)(Cb,Ta)2O6 An iron-black mineral with a submetallic luster that crystallizes in the orthorhombic system; the chief ore mineral of niobium (columbium); hardness is 6 on Mohs scale, and specific gravity is 5.4-6.5. Also known as dianite; greenlandite; niobite.



(from Latin columbium, an alternate name for niobium), a mineral of the columbite-tantalite group, combining complex oxides of the AB2O6 type and forming the isomorphic series FeNb2O6—MnNb2O6 (columbite proper) and FeTa2O6—MnTa2O6 (tantalite). The columbites also include members of isomorphic series in which niobium (in weight percent) predominates over tantalum.

The varieties of columbite include tantalocolumbite (20–40 percent Ta2O5), ferrocolumbite (FeO : MnO > 3 : 1), manganocolumbite (MnO : FeO > 3:1), magnesiocolumbite (FeO < MgO > MnO), and ixiolite (to 13 percent SnO2). In addition to the basic components, columbite almost always contains admixtures of titanium, tungsten, rare earth elements, uranium, thorium, and zirconium. Columbite crystallizes in the rhombic system. Its structure is based on the closest possible hexagonal (double-layered) packing of oxygen atoms, in the alternating layers of which the octahedral spaces are occupied in turn by (Nb, Ta) and (Fe, Mn). Columbite crystals are short prismatic, thin tabular, or tabular. They are black, brownish black, or, less often, reddish brown (manganocolumbites). The hardness of columbite is 6.0 on the mineralogical scale; the density, 5,150–6,350 kg per cu m (tantalocolumbites). Genetically, columbite is related to the quartz-bearing subalkaline syenites and the acidic alaskites, biotites, and binary granites, and particularly, to their pegmatitic and postmagmatic pneumatolytic and hydrothermal derivatives. Columbite is a source of niobium.

References in periodicals archive ?
5-cm samarskite crystals which sit in a matrix of red feldspar, with grains of columbite.
Pyrochlore and columbite are both present, together with some rare-earth enriched dikes.
Minerals besides fluorite that have been found as inclusions in topaz are quartz, feldspar, albite, columbite, elpasolite and smoky quartz.
The other heavy minerals can be ilmenite, magnetite, columbite, zircon, monazite, and garnet, among others.
Tantalite is the most widespread tantalum mineral and forms a series with the mineral columbite.
He enthusiastically told me about a fabulous mine there that had 3-foot fluorite crystals and sprays of columbite and tantalite in the walls of the mine.
Pegmatite-Mine Farm Name Economic Minerals Sandamap Sandamap Cassiterite; ferrotantalite North 115 Cameroon pegmatite Goabeb 63 Cassiterite-equivalent to Sandamap Sidney pegmatite Davib West 62 and Cassiterite; lepidolite northern boundary with Goabeb 63 Borna pegmatite Davib Ost 61 Cassiterite Carsie pegmatite Davib Ost 61 Cassiterite; ferberite; columbite (Fe?
This good news spurred further searching which turned up large quantities of fluorite, muscovite, magnetite, menaccinite, molybdenite, graphite, columbite, allanite, several more pounds of fergusonite and ultimately over 200 pounds of gadolinite.
On the return trip we stopped to rest on the shallow bank of a river, and saw local people washing the sand for black columbite crystals.