Editorial Feature

Cobaltite - Occurrence, Properties, and Distribution

Cobaltite is a sulfosalt mineral, containing sulfur, arsenic, and cobalt. It was discovered as early as 1832 from mines in the Cobalt district, Ontario, Canada.

The mineral was named after the German word Kobold, which means "underground spirit" or "goblin”, representing its elemental composition.

Properties of Cobaltite

The following are the key properties of Cobaltite:

  • Cell Data
    • Space Group: Pca21
    • a = 5.5833(7)
    • b = 5.5892(6)
    • c = 5.5812(8)
    • Z = 4

  • Crystal Data
    • Orthorhombic, pseudocubic
    • Point Group: mm2
    • Commonly as pseudocubic or pseudopyritohedral crystals, or combinations having striated faces as with pyrite, to as large as 8cm, also as pseudo-octahedra; granular massive
    • Twinning: About [111] as a pseudocubic three-fold axis, with {011} and {111} of the pseudocubic habit as twin planes, rare. Twin lamellae are commonly observed in polished section, which may exhibit a flame-like texture
    • X-ray Powder Pattern: 2.49 (100), 1.680 (100), 2.27 (90), 2.77 (80), 1.490 (80), 1.073 (80), 1.973 (60)

  • Chemical Composition
    Elements Content 1 Content 2 Content 3
    Co 28.64 33.2 35.53
    Fe 4.11 2.8 -
    Ni 3.06 0.6 -
    As 44.77 43.4 45.15
    S 19.34 20.6 19.32
    Total 99.92 100.6 100.00

  • Optical Properties
    • Pleochroism: Very weak, on grain boundaries
  • Estimated Properties
    Electron density Bulk density (electron density) = 5.82 g/cm3
    note: Specific gravity of Cobaltite = 6.35 g/cm3
    Photoelectric PECobaltite = 45.56 barns/electron
    U = PECobaltite x ρElectron density = 265.02 barns/cm3
    Fermion index Fermion index = 0.001
    Boson index = 0.998
    Cobaltite is not radioactive

How to Identify Cobaltite

Cobaltite can be identified in the field by a range of colors, from reddish-silver-white, to violet-steel-gray, and black. It is opaque, non-fluorescent, and magnetic after heating. Its fractures are brittle, as that of non-metallic minerals and glasses. The mineral occurs as anhedral to subhedral crystals, with parallel lines on the crystal surface.

It has a density of 6.33 g/cm3, and a hardness of 5.5.

Global Distribution

Cobaltite is distributed in the following places:

  • Tunaberg, Sodermanland, Sweden
  • Riddarhyttan and Hakansboda, Vastmanland
  • Vena mines, near Askersund, Orebro
  • Skutterud, Modum, Norway
  • Bieber, near Hanau, Hesse, Germany
  • Crown’s Engine House, Wheal Cock
  • Botallack mine, St. Just, Cornwall, England
  • Mines in the Cobalt and Sudbury districts, Ontario
  • Great Bear Lake, Northest Territories, Canada
  • Broken Hill and Torrington, New South Wales, Australia
  • Bimbowrie, South Australia
  • Mt. Cobalt and Cloncurry, Queensland
  • Ait Ahmane mine, Bou Azzer, Morocco

Occurrence of Cobaltite and Useful Mineral Association

Cobaltite occurs in high-temperature hydrothermal deposits, as veins in contact metamorphosed rocks, and as disseminations.

Calcite, titanite, scapolite, zoisite, allanite, skutterudite, chalcopyrite, sphalerite, and magnetite are the minerals that are analogous to cobaltite.


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