Brassite - Occurrence, Properties, and Distribution

Brassite is a rare arsenate mineral, first discovered in 1973 in Jachymov (Joachimsthal), Czech Republic. The mineral was named after Rejane Brasse, who first synthesized the compound.

Properties of Brassite

The following are the key properties of Brassite:

  • Cell Data
    • Space Group: Pbca (synthetic)
    • a = 7.472(1)
    • b = 10.891(1)
    • c = 16.585(5)
    • Z = 8

  • Crystal Data
    • Orthorhombic
    • Point Group: 2/m 2/m 2/m
    • Cryptocrystalline crusts and powder, intermixed with other arsenates
    • X-ray Powder Pattern: 4.97 (10), 3.20 (8), 3.07 (7), 4.14 (6), 3.88 (5), 2.324 (5), 4.54 (4)

  • Chemical Composition
    Elements Content 1 Content 2
    As2O5 48.1 48.63
    H2O 35.4 34.31
    MgO 15.6 17.06
    CaO 0.9 -
    Total 100 100

  • Optical Properties
    • Optical Class: Biaxial (+) (synthetic)
    • Orientation: X = b; Y = a; Z = c
    • α = 1.531(2)
    • β = 1.546(2)
    • γ = 1.562(2)
    • 2V(meas.) = n.d.
    • 2V(calc.) = 80°

  • Estimated Properties
    Electron density Bulk density (electron density)=2.33 g/cm3
    note: Specific gravity of Brassite =2.33 g/cm3
    Photoelectric PEBrassite = 20.91 barns/electron
    U= PEBrassite x ρ Electron density= 48.66 barns/cm3
    Fermion index Fermion index = 0.01
    Boson index = 0.99
    Radioactivity
    Brassite is not radioactive

How to Identify Brassite

Brassite is a white mineral, having white streak and perfect cleavage. The density of brassite is 2.28 g/cm3.

Global Distribution

Brassite is distributed in the following places:

  • Jachymov (Joachimsthal), Czech Republic
  • Bieber and Richelsdorf, Hesse, and Wittichen, Black Forest, Germany
  • Ruben mine, Kohlendorf, Nowa Ruda (Neurode), Silesia, Poland
  • Salsigne mine, 15km north of Carcassone, Aude, France

Occurrence of Brassite and Useful Mineral Association

Brassite occurs as a rare reaction product of arsenic-rich solutions with Ca–Mg carbonates. It is closely associated with dolomite, realgar, arsenic, rauenthalite, haidingerite, weilite, picropharmacolite, and pharmacolite.

References

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