Columbite-(Fe)
Mineral FeNb2O6
Also called Ferrocolumbite, Niobite, and Coltan (in part)
About it
Heavy, black, blocky to tabular crystals with a dark brown streak, in granite pegmatites. With tantalite it makes up coltan, the ore of niobium and tantalum; good crystals come from Brazil, Madagascar, and the Black Hills.
- Type
- Mineral
- Group
- Oxide, columbite group
- Formula
- FeNb2O6
- Hardness (Mohs)
- 6
- Specific gravity
- 5.3–7.3
- Streak
- blackish brown
- Lustre
- submetallic, resinous
- Crystal system
- Orthorhombic
- Colours
- black, brownish black
- Transparency
- opaque
- Cleavage and fracture
- distinct in one direction; subconchoidal to uneven fracture
Typical values: real specimens vary. For more, see mindat.org.