Columbite

Probably Columbite-Fe

Mineral formula: Fe²⁺Nb₂O₆ to Mn²⁺Nb₂O₆

Mineral group: member of the Columbite group

Crystal system: orthorhombic

Crystal habit: Short prismatic or equant, also flat tabular

Cleavage: distinct on {100], less distinct on {010]

Fracture: irregular/uneven, subconchoidal

Color: black to brownish black

Luster: vitreous to sub-metallic

Diaphaneity: opaque

Moh’s scale hardness: 6

Streak: black to dark brown

Specific gravity: 5.2 – 6.65

Named: in 1801 by Charles Hatchett (1765-1847) from a specimen collected in the mid-17th century in a place called Nautneague (now regarded as Haddam, Connecticut, USA). The specimen was from the mineral collection of John Winthrop (1606–1676), governor of Connecticut and was given to Hans Sloane by John Winthrop (1681–1747) who was the grandson of the governor with the same name. From the type specimen, Hatchett named the new element columbium (now called niobium). The current species, columbite-(Fe) retains the old root name and has the suffix -(Fe) to indicate the dominance of iron in the species. Columbite was the second species named from the USA, after celestine (q.v.)