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There are three columbites:
columbite-(Fe): Fe2+Nb2O6,
columbite-(Mg): MgNb2O6, and
columbite-(Mn): Mn2+Nb2O6
All of these are multiple oxides containing niobium, and members of the
columbite group
Specific gravity: 5.3 to 8.1
Hardness: 6
Streak: Brown to black
Colour: Brownish black to black
Solubility: Insoluble in hydrochloric and nitric acid; slightly soluble in sulphuric acid
Environments:
Plutonic igneous environments
Pegmatites
Carbonatites
Columbite occurs in granitic rocks and
pegmatites, associated with
quartz,
feldspars,
mica,
tourmaline,
beryl,
spodumene,
cassiterite,
hübnerite-ferberite,
microlite and
monazite.
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