Caledonite – Occurrence, Properties, and Distribution

Caledonite was named after ‘Caledonia’, the Roman name for the Highlands of Scotland, where the mineral was first discovered.

Properties of Caledonite

The following are the key properties of caledonite:

  • Cell Data
    • Space group: Pnm21
    • a = 7.146(3)
    • b = 20.089(7)
    • c = 6.560(5)
    • Z = 2

  • Crystal Data
    • Orthorhombic
    • Point group: mm2
    • As striated prismatic [001] crystals, to 2.5cm, typically flattened on {100} and displaying many forms, including {010}, {100}, {120}, {101}, {131}, {011}, {111}, {121}
    • In divergent aggregates, rarely fibrous
    • as massive coatings
    • X-ray powder pattern: 3.139 (100), 4.69 (57), 3.031 (55), 1.861 (55), 2.752 (43), 3.152 (36), 2.226 (36)

  • Chemical Composition
    Elements Content 1 Content 2
    PbO 69.18 69.17
    SO3 14.15 14.89
    CuO 9.73 9.86
    H2O 3.78 3.35
    CO2 3.16 2.73
    Total [100.00] 100.00

  • Optical Properties
    • Optical class: Biaxial (-)
    • Pleochroism: Weak
    • Orientation: X = c; Y = a; Z = b
    • Dispersion: r < v, barely perceptible
    • α = 1.818(3); β = 1.866(3); γ = 1.909(3)
    • 2V(meas.) = ~85°

  • Estimated Properties
    Electron density Bulk density (electron density) = 4.91 g/cm3
    note: Specific gravity of caledonite = 5.69 g/cm3
    Photoelectric PECaledonite = 1,146.78 barns/electron
    U = PECaledonite x ρ electron density = 5,629.99 barns/cm3
    Fermion index Fermion index = 0.14
    Boson index = 0.86
    Radioactivity
    Caledonite is not radioactive

How to Identify Caledonite

Caledonite can be identified in the field by its color variations, such as blue, blue-green, green, and dark green. Its transparent to translucent form has {001} perfect and {100} distinct cleavage. This mineral has a vitreous–greasy luster, with greenish-white streak. The fracture on this mineral is uneven - flat surfaces.

The density of caledonite is 5.7 to 6.4 g/cm3, with a hardness of 2.5 to 3 - between finger nail and calcite. It is non-fluorescent.

Global Distribution

Caledonite is distributed in the following places:

  • Scotland - From Leadhills, Lanarkshire, and Wanlockhead, Dumfrieshire
  • England - At Red Gill and other mines, Caldbeck Fells, Cumbria
  • Australia - From Paddy’s River mine, Australian Capital Territory
  • Russia - In the Preobrazhensky mine, Beresovsk, near Yekaterinburg (Sverdlovsk), Middle Ural Mountains
  • Iran - Large crystals from Tchah Milleh, Anarak
  • USA - In Arizona, large crystals in rich masses from the Mammoth-St. Anthony mine, Tiger, Pinal Co. in the Rowley mine, near Theba, Maricopa Co. and elsewhere; from the Mex-Tex mine, near Bingham, Hansonburg district, Socorro Co. New Mexico; large crystals from the Blue Bell mine, near Baker, San Bernardino Co. at the Chance mine, Chidago Canyon, Mono Co. and from Cerro Gordo, Inyo Co. California
  • Chile - At Challacollo, Tarapaca

Occurrence of Caledonite and Useful Mineral Association

Caledonite occurs in an uncommon secondary mineral in the oxidized portions of Pb–Cu deposits.

It is often associated with minerals such as cerussite, anglesite, azurite, leadhillite, brochantite, linarite, and malachite.

References

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