Editorial Feature

Microlite – Occurrence, Properties and Distribution

Microlite was discovered in the year 1835 at the Clark Ledge pegmatite locality Massachusetts, USA. The name of this mineral is derived from the Greek word for the size of the crystals when found at the original location.

Properties of Microlite

The key physical properties of Microlite are as below:

  • Cell Data
    • Space Group = Fd3m
    • a = 10.36-10.46
    • Z = 8
  • Crystal Data
    • Cubic.
    • Point Group – 4/m 3 2/m.
    • Crystals – commonly as euhedral to subhedral octahedral, modified by the dodecahedron cube, and {113} to 8 cm; also granular, massive.
      Twinning: rare, according to the spinel law, twin plane {111}.
    • X-ray powder pattern: Onca, Brazil.
      1.568 (100), 1.838 (84), 3.00 (68), 1.193 (68), 1.000 (68), 1.354 (63), 1.163 (63).
  • Chemical Composition
    Elements Content 1 Content 2
    Nb2O5 - 3.4
    Ta2O5 73.72 77.9
    TiO2 1.58 1.1
    SnO2 - 1.1
    UO2 4.21 -
    RE2O3 0.5 -
    FeO 2.77 -
    MnO - 0.2
    MgO 0.34 -
    CaO 10.48 15.7
    Na2O 3.26 0.7
    K2O 0.64 -
    H2O 2.72 -
  • Optical Properties
    • Opaque, Transparent in thin sections.
    • Lustre – vitreous to adamantine, resinous on fractures.
    • Color - pale yellow to brown, hyacinth-red, greenish yellow, grass green, emerald green, white, gray, black, colourless, yellow.
    • Optical Class – Isotropic.
    • n = 1.93-2.02.
  • Estimated Properties
    Electron density Bulk density (electron density) = 5.39 g/cm3
    note: Specific gravity of Microlite = 6.23 g/cm3
    Photoelectric PEMicrolite = 814.71 barns/electron
    U = PEMicrolite x ρelectron density = 4392.35 barns/cm3
    Fermion index Fermion index = 0.0002
    Boson index = 0.99

    Radioactivity

    GRapi = 0 (Gamma Ray American Petroleum Institute Units)
    Microlite is not radioactive.

How to Identify Microlite

The color of microlite varies from pale yellow to brown; the other colors in which microlite appears are hyacinth-red, greenish yellow, grass green, emerald green, white, gray, black, colourless, yellow. It is brittle by nature, having a hardness that varies from 5-5.5.

Global Distribution

Microlite is a mineral that is found in a number of locations, but only a few locations have large crystal deposits of this mineral. Some of the main locations are as below:

  • USA – from Chesterfield, Massachusetts; Middletown, Conneticut; large crystals at Amelia, Virginia; Harding mine, New Mexico; Gunnison Co, Colorado.
  • Norway – from Iveland district.
  • Mozambique – from Alto Ligonha district.
  • Brazil – from Paraiba, Onca, large crystals from Virgem da Lapa, Minas Gerais.
  • Western Australia – from Wodgina and Greenbushes.

Occurrence of Microlite and Useful Mineral Association

Microlite occurs as a primary mineral in lithium bearing granite pegamites, or replacing tantalum minerals; in miarolitic cavities in granites.

Some of the minerals with which microlite is associated with are fluorite, tantalite, topaz, beryl, lepidolite, albite and tourmaline.

References

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