Mineral Information and Data:

Columbite-(Fe)
Fe2+Nb2O6 [CNMNC approved formula]

Named as the ferrous-dominant member of the columbite group. First published in 1805 as columbite (from COLUMBia, for America, source of the first specimen) , then as ferrocolumbite to emphasize its iron content in 1915. Name changed from ferrocolumbite (IMA, 2008) and columbite becomes a group name.

IMA status : Renamed IMA Approved; 2008 ()
CLASSIFICATION 
Dana
(8th edition) :
08.03.02.02  
  (08) Multiple Oxides with Nb, Ta, and Ti
  (08.03) where A (B2O6)
  (08.03.02) Tantalite - Columbite Series
  
Nickel-Strunz
(10th edition) :
04.DB.35
  (04) Oxides and Hydroxides
  (04.D) Metal:Oxygen = 1:2 and similar
  (04.DB) With medium-sized cations; chains of edge-sharing octahedra
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Space group: Pbcn
Unit cell: a = 14.266(1) Å, b = 5.7321(4) Å, c = 5.0503(4) Å
Crystal Habit: Crystals short prismatic or equant, also flat tabular. In groups of parallel or subparallel crystals; massive.
Twinning: Common as heart-shaped contact and penetration twins, on {021} and {023}, may produce pseudohexagonal trillings.
  
Color: Black to brownish black; reddish brown in transmitted light; in reflected light, grayish white with a brownish tint and reddish internal reflections
Diaphaneity: Opaque, translucent through thin edges
Luster: Submetallic to vitreous, commonly tarnished iridescent
Hardness (Mohs): 6
Measured Density: 5.20 – 6.65 g/cm3
Cleavage: Distinct on {100}, less distinct on {010}
Tenacity: Brittle
Fracture: Subconchoidal to uneven
Streak: Black to dark brown
  
Polymorphism and Series: Forms two series, with tantalite(Fe) and with columbite(Mn).
Geologic Setting: An accessory constituent of granite pegmatites; rarely in carbonatites; a detrital mineral in placer deposits.
Mineral Association: Albite, microcline, beryl, lepidolite, muscovite, tourmaline, spodumene, lithiophilite, triphylite, amblygonite, triplite, apatite, samarskite, microlite, cassiterite.
  
Other Properties: Paramagnetic (weakly attracted to magnetic fields).

 

Columbite-(Fe)
Origin: Mahaiza, Betafo, Antsirabé region,
Antananarivo Province, Madagascar
Sample size: 4.6 x 3.7 x 2.5 cm
Photo: John Veevaert, Trinity Mineral Co.

 

Columbite-(Fe)
(zoom-in of above)

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