Freedite - Occurrence, Properties, and Distribution

Freedite is a monoclinic-prismatic mineral containing oxygen, lead, copper, chlorine, and arsenic. It was named after Dr. Robert L. Freed, an American mineralogist from Trinity University, San Antonio, Texas, USA.

Chemical Formula – Pb8Cu+(As+++O3)2O3Cl5

Properties of Freedite

The following are the key properties of freedite:

  • Cell Data
    • Space Group: C2/m
    • a = 13.578(2)
    • b = 20.099(3)
    • c = 7.465(1)
    • β = 105.73(1)°
    • Z = 4
  • Crystal Data
    • Monoclinic, pseudotetragonal
    • Point Group: 2/m
    • As composite crystals in slightly radial aggregates
    • X-ray Powder Pattern: 2.949 (10), 2.830 (8), 2.734 (8), 3.832 (5), 2.096 (5), 6.51 (4), 3.581 (4)
  • Chemical Composition
    Elements Content 1 Content 2
    PbO 80.2 81.45
    As2O3 9.2 9.02
    Cl 8.0 8.09
    CuO 4.9 3.26
    -O = Cl2 1.8 1.82
    FeO 0.4 -
    Total 100.9 100

 

Content 1: Langban, Sweden; by electron microprobe, total Cu as CuO, total Fe as FeO, total As as As2O3; neglecting H2O + CO2 0.2% by TGA-EGA-mass spectrometer, corresponds to Pb29.4Cu2+ 5.1 Fe2+ 0.5As3+ 7.6Cl18.4O37.1.
Content 2: Pb8Cu(AsO3)2O3Cl5.

  • Optical Properties
    • Optical Class: Biaxial
    • Pleochroism: Weak to none
    • α = > 1.90
    • β = > 1.90
    • γ = > 1.90
    • 2V(meas.) = n.d.
  • Estimated Properties
    . .
    Electron density Bulk density (electron density) = 5.80 g/cm3
    note: Specific gravity of freedite = 7 g/cm3
    Photoelectric PEFreedite = 1408.62 barns/electron
    U= PEFreedite x ρElectron density = 8168.02 barns/cm3
    Fermion index Fermion index = 0.16
    Boson index = 0.84
    Radioactivity Freedite is not radioactive.

 

How to Identify Freedite

Freedite is a greenish-yellow mineral having perfect cleavage, a vitreous/glassy luster, and a yellow streak. It can be formed as aggregate made of numerous individual radial crystals or clusters: its crystals radiate from a center without producing stellar forms. The density of Freedite is 7 g/cm3, and its hardness is 3.

Global Distribution

Freedite is widely distributed at L°ngban, Värmland, Sweden.

The occurrence of Freedite and Useful Mineral Association

Freedite occurs as an uncommon mineral in andradite–magnetite ore of a metamorphosed Fe–Mn ore body. It is closely related to magnetite, andradite, calcite, finnemanite, copper, lead, and ecdemite.

This article was updated on 27th February, 2020.

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