Mineral Information and Data:

Columbite-(Mn)
Mn2+Nb2O6 [CNMNC approved formula]

Named as the maganese-dominant member of the columbite group. First published in 1892. Name changed from manganocolumbite (IMA, 2008)

IMA status : Renamed IMA Approved; 2008 ()
CLASSIFICATION 
Dana
(8th edition) :
08.03.02.04  
  (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 = 14.433(2)Å, b = 5.7637(7)Å, c = 5.0832(8)Å, Z=4
Crystal Habit: Crystals short prismatic or equant, also tabular; in groups of parallel or subparallel crystals; massive.
Twinning: 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, with reddish brown internal reflections
Diaphaneity: Opaque, translucent through thin edges
Luster: Submetallic to vitreous
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: Dark red to black
  
Polymorphism and Series: Forms two series, with columbite(Fe), and with tantalite(Mn).
Geologic Setting: As an accessory and primary constituent of granite pegmatites; detrital in placers.
Mineral Association: Albite, microcline, beryl, lepidolite, muscovite, tourmaline, spodumene, lithiophilite, triphylite, amblygonite, triplite, apatite, samarskite, microlite, cassiterite
  

 

Columbite-(Mn)
Fragment consisting of multiple phases.
Mineral identification confirmed by X-ray diffraction and chemical analysis.
Origin: Mina Miramica, Santa Cruz, Bolivia.
Photo: © RRUFF Project

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