Columbite, also called niobite, niobite-tantalite and columbate [(Fe, Mn)Nb2O6], is a black mineral group that is an ore of niobium. It is a black mineral, typically occurring as dense tabular crystals, consisting of an oxide of iron, manganese, niobium, and tantalum. It has a submetallic luster and a high density and is a niobate of iron and manganese. It is the chief ore of niobium. is the most widespread niobium mineral and makes for an important ore of the industrially useful metal.
- Category: Oxide minerals
- Formula: Fe2+Nb2O6
- Crystal system: Orthorhombic
- Crystal class: Dipyramidal (mmm)
Columbite has the same composition and crystal symmetry (orthorhombic) as tantalite. It is also very similar to tapiolite. Those minerals have same chemical composition but different crystal symmetry: orthorhombic for columbite and tetragonal for tapiolite. The largest documented single crystal of columbite consisted of plates 6 mm (0.24 in) thick measuring 76 cm × 61 cm (30 in × 24 in).
- Color: Black, brownish black.
- Crystal habit: Massive – Granular – Common texture observed in granite and other igneous rock; Striated – Parallel lines on crystal surface or cleavage face.
- Mohs scale hardness: 6
- Luster: sub-metallic
- Streak: blackish brown
- Specific gravity: 5.3–7.3, Average = 6.3
This mineral group was first found in Haddam, Connecticut, in the United States. It forms a series with the tantalum-dominant analog ferrotantalite and one with the manganese-dominant analog manganocolumbite. The iron-rich member of the columbite group is ferrocolumbite. Some tin and tungsten may be present in the mineral.