Colemanite - Occurrence, Properties, and Distribution

Colemanite is a borate mineral, which forms by the alteration of ulexite and borax.

It was first discovered in 1884 from the Furnace Creek in Death Valley. The mineral was named after William Tell Coleman, owner of Harmony Borax mine where the mineral was first found.

Properties of Colemanite

The following are the key properties of Colemanite:

  • Cell Data
    • Space Group: P21/a
    • a = 8.712(2)
    • b = 11.247(3)
    • c = 6.091(1)
    • β = 110.12(2)°
    • Z = 2

  • Crystal Data
    • Monoclinic
    • Point Group: 2/m
    • As equant to short prismatic crystals, with large {110} and multiple terminating forms, to 30cm; pseudorhombohedral, with large {110} and {301}; pseudo-octahedral, with large {221} and {011}; nearly 50 forms measured; cleavable massive, granular, most commonly nodular
    • X-ray Powder Pattern: 3.13 (100), 5.64 (50), 3.85 (50), 2.550 (50), 2.010 (50), 4.00 (36), 3.29 (36)

  • Chemical Composition
    Elements Content 1 Content 2
    B2O3 50.70 50.81
    CaO 27.31 27.28
    H2O 21.87 21.91
    MgO 0.10
    Total 99.98 100.00

  • Optical Properties
    • Optical Class: Biaxial (+)
    • Orientation: X = b; Y ^ c = --6°; Z ^ c = 84°
    • Dispersion: r > v, weak
    • α = 1.586
    • β = 1.592
    • γ = 1.614
    • 2V(meas.) = 56°

  • Estimated Properties
    Electron density Bulk density (electron density) = 4.69 g/cm3
    note: Specific gravity of Colemanite = 4.91 g/cm3
    Photoelectric PEColemanite = 21.27 barns/electron
    U = PEColemanite x ρElectron density = 99.79 barns/cm3
    Fermion index Fermion index = 0.01
    Boson index = 0.99
    Radioactivity
    Colemanite is not radioactive

How to Identify Colemanite

Colemanite can either be colorless, or can be found in a range of colors including white, yellowish-white, gray, and gray-white. It has a transparent to translucent appearance, perfect cleavage, white streak, and vitreous luster. It is fluorescent in nature, and its fractures appear brittle. It can be formed as massive crystals that are granular and coarse.

The relative hardness of colemanite is 4.5, and its density is 2.42 g/cm3.

Global Distribution

Colemanite is distributed in the following places:

  • Death Valley, Death Valley, near Ryan, Furnace Creek district, California
  • Borate, about 10km north-east of Yermo, Calico Hills, San Bernardino Co.
  • Anniversary mine, Muddy Mountains district, Clark Co. Nevada
  • Penobsquis and Salt Springs evaporite deposits, near Sussex, New Brunswick, Canada
  • El Torreon and La Tinaja del Oso, near Magdalena, Sonora, Mexico
  • Salinas Grandes Playa, Argentina
  • Loma Blanca deposit, 8km south-west of Coranzuli, Jujuy Province
  • Sijes district, Salta Province
  • Inder borate deposit, Kazakhstan
  • Bela Stena, Jarandol Basin, Serbia, Yugoslavia
  • Lake on West Samos Island, Greece
  • Extensive deposits in Turkey, as in the Bigadic borate district, Balikesir Province
  • Kestelek borax deposit, Eski¸cehir Province
  • Emet borate deposits, Kutahya Province
  • Mustafakemalpasa, Bursa Province

Occurrence of Colemanite and Useful Mineral Association

Colemanite occurs as a common constituent in borate deposits, formed in arid alkaline lacustrine environments that are deficient in carbonate and sodium.

It is closley associated with celestine, calcite, gypsum, kernite, luneburgite, gowerite, ginorite, nobleite, priceite, searlesite, ulexite, and howlite.

References

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