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
|-O = Cl2
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
||Bulk density (electron density) = 5.80 g/cm3
note: Specific gravity of freedite = 7 g/cm3
||PEFreedite = 1408.62 barns/electron
U= PEFreedite x ρElectron density = 8168.02 barns/cm3
||Fermion index = 0.16
Boson index = 0.84
||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.
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.