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columbite




columbite
Columbite. Credit:Smithsonian Institution
A lustrous black oxide mineral of iron, manganese, and niobium [(Fe, Mn) Nb2O6]. It is the chief ore of niobium and is found in granite pegmatites mainly in Western Australia, Zaire, Madagascar, and South Dakota. Tantalum replaces niobium in all proportions up to 100% (tantalite). Columbite crystallizes in the orthorhombic system, forming prismatic crystals with one distinct cleavage. Hardness 6.0 to 6.5. Relative density 5.2 (columbite) to 8.0 (tantalum).


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