Arsenopyrite - Occurrence, Properties, and Distribution

Arsenopyrite is an iron arsenic sulfide mineral which is the most common arsenic-bearing mineral found worldwide. The mineral was named for the presence of arsenic in its composition.

Properties of Arsenopyrite

The following are the key properties of Arsenopyrite:

  • Cell Data
    • Space Group: P21/c
    • a = 5.744(2)
    • b = 5.675(1)
    • c = 5.785(2)
    • β = 112.17(2)°
    • Z = 4.
  • Crystal Data
    • Monoclinic, pseudo-orthorhombic.
    • Point Group: 2/m.
    • Crystals, to 30 cm, flat tabular to blocky to prismatic, striated || [001]. Also compact, granular, columnar.
    • Twinning: Common on {100} and {001}; as contact or penetration twins on {101}; on {012} to produce star-shaped trillings or cruciform twins.
    • X-ray Powder Pattern: 2.677 (100), 2.662 (100), 2.418 (95), 2.412 (95), 2.440 (90), 1.814 (90), 1.824 (70).
  • Chemical Composition
    Elements Content 1 Content 2 Content 3
    As 44.34 48.72 46.01
    Fe 34.53 32.48 34.3
    S 20.22 18.80 19.69
    Bi 0.79 - -
    Co 0.09 1.16 -
    Total 99.97 101.16 100
  • Optical Properties
    • Pleochroism: Weak, in white or bluish tint and faint reddish yellow.
    • Anisotropism: Strong, red-violet.
  • Estimated Properties
    Electron density Bulk density (electron density) = 5.70 g/cm3
    note: Specific gravity of Arsenopyrite = 6.19 g/cm3
    Photoelectric PEArsenopyrite = 44.13 barns/electron
    U = PEArsenopyrite x ρ Electron density = 251.61 barns/cm3
    Fermion index Fermion index = 0.0087
    Boson index = 0.99
    Radioactivity

    Arsenopyrite is not radioactive.

How to Identify Arsenopyrite

Arsenopyrite is a light steel gray or tin white mineral having a black streak, metallic luster, opaque appearance, and non-fluorescent characteristic. Arsenopyrite exhibits distinct cleavage and brittle fractures as displayed by glasses and most non-metallic minerals. The mineral can be formed as prismatic or euhedral crystals. The density of arsenopyrite is 6.07 g/cm3, and its hardness is 5.

Global Distribution

Arsenopyrite is distributed in the following places:

  • Altenberg, Ehrenfriedersdorf, and Freiberg, Saxony, Germany
  • Stari Trg mine, Trepca, Serbia
  • Panasqueira, Portugal
  • Sala, Tunaberg, Stollberg, Boliden, and Nordmark, Sweden
  • Stratonik, Greece
  • Cornwall, and in Devonshire, at Tavistock, England
  • Franconia, Grafton Co., New Hampshire and Franklin, Sussex Co., New Jersey, USA
  • Hidalgo del Parral and Santa Eulalia, Chihuahua, Mexico
  • Cobalt district, Ontario, Canada
  • Obira mine, Bungo, Oita Prefecture, Japan
  • Ashio mine, Tochigi Prefecture, Japan.

Occurrence of Arsenopyrite and Useful Mineral Association

Arsenopyrite occurs in pegmatites, high-temperature gold-quartz and tin veins. This mineral can be also observed in contact metamorphic sulfide deposits, gneisses, schists and other metamorphic rocks. It is closely associated with cassiterite, scheelite, gold, galena, chalcopyrite, pyrite and pyrrhotite.

References

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