Columbite
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NameColumbite
Chemical Formula(Fe,Mn)Nb2O6
Mohs Hardness6
Crystal Systemorthorhombic
Lustervitreous
Streak Colordark red to black
Cleavagegood in one direction ({100})
Fracturesubconchoidal to uneven
Specific Gravity6
Colorsblack, brownish-black, dark brown
Transparencyopaque
Type LocalityMiddletown, Middlesex County, Connecticut, USA
Mineral GroupOxides
Usessource of niobium, collector's specimens
Associated Mineralsquartz, feldspar, mica, beryl, tourmaline, spodumene, cassiterite, tantalite
Rarityuncommon
Description
A dark, blocky, submetallic crystal, likely black or very dark brown, with a somewhat rectangular or tabular habit, measuring approximately 3.5 cm.
Geological Context
Columbite typically forms in granite pegmatites and is often associated with other rare-earth minerals. It can also be found in placer deposits.
