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Dolomite - Occurrence, Properties, and Distribution

Dolomite is a carbonate mineral, consisting of calcium magnesium carbonate. It was first described as the ‘stinking stone’ by Belsazar Hacquet, an Austrian naturalist. Later, Déodat Gratet de Dolomieu, a French naturalist and geologist, described it as a rock from the Dolomite Alps in Italy.

Properties of Dolomite

The following are the key properties of Dolomite:

  • Cell Data
    • Space Group: R3
    • a = 4.812(1)
    • c = 16.020(3)
    • Z = 3

  • Crystal Data
    • Hexagonal
    • Point Group: 3
    • Crystals, typical combinations of {1011} and {1120}, tabular on {0001}, many minor forms, may exhibit curved faces, to 20cm
    • Saddle-shaped aggregates, columnar, stalactitic, granular, massive
    • Twinning: With {0001}, {1010}, or {1120} as twin plane, common as simple contact twins and in combinations; lamellar on {0221}
    • X-ray powder pattern: 2.886 (100), 2.192 (30), 1.783 (30), 1.804 (20), 2.015 (15), 1.389 (15), 2.670 (10)

  • Chemical Composition
    Elements Content 1 Content 2
    CO2 47.22 47.73
    CaO 31.27 30.41
    MgO 21.12 21.86
    FeO 0.22
    SiO2 0.12 -
    H2O 0.02 -
    Total 99.97 100.00

  • Optical Properties
    • Optical Class: Uniaxial (–), anomalously biaxial
    • Dispersion: Very strong
    • ω = 1.679
    • ε = 1.500
    • 2V(meas.) = Small
  • Estimated Properties
    Electron density Bulk density (electron density)=2.83 g/cm3
    note: Specific gravity of Dolomite =2.84 g/cm3
    Photoelectric PEDolomite = 3.13 barns/electron
    U= PEDolomite x ρElectron density= 8.86 barns/cm3
    Fermion index Fermion index = 0.01
    Boson index = 0.99
    Radioactivity
    Dolomite is not radioactive

How to Identify Dolomite

Dolomite occurs in white, gray, reddish-white, or brownish-white forms. It has a transparent to translucent appearance. It is a non-fluorescent mineral with a vitreous lustre, a white streak and perfect cleavages.

The fractures are brittle and blocky, producing small, conchoidal fragments. Its crystals are coarse and massive. The average density of dolomite is 2.84 g/cm3, and its relative hardness ranges from 3.5 to 4.

Global Distribution

Dolomite is distributed in the following places:

  • Traversella and Brosso, Piedmont, Italy
  • Eugui, Navarra Province, Spain
  • Trieben and Hall, Tirol, Austria
  • Freiberg and Schneeberg, Saxony, Germany
  • Lengenbach, Binntal, Switzerland
  • Trepca, Serbia, Yugoslavia
  • Frizington, Cumbria, England
  • Vuoriyarvi carbonatite complex, Kola Peninsula, Russia
  • Brumado, Bahia
  • Morro Velho gold mine, Nova Lima, Minas Gerais, Brazil
  • Naica, Chihuahua, Mexico
  • Lockport, New York, USA
  • Stony Point, Alexander Co. North Carolina
  • Mississippi Valley region, in the Tri-State district, at Joplin
  • Jasper Co. Missouri
  • Galena, Cherokee Co. Kansas
  • Picher, Ottawa Co. Oklahoma

Occurrence of Dolomite and Useful Mineral Association

Dolomite is formed by diagenesis, or the hydrothermal metasomatism of limestone. It occurs in a primary phase in hypersaline sedimentary environments, ultramafic rocks, and carbonatites. It also occurs as a major component of certain contact metamorphic rocks and marbles, and a gangue in hydrothermal veins.

It is closely associated with apatite, siderite, ankerite, calcite, wollastonite, forsterite, tremolite, diopside, magnetite, magnesite, serpentine, talc, quartz, gypsum, celestine, metal sulfides, barite and, fluorite.

References

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