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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.