Calcite – Occurrence, Properties, and Distribution

Calcite was named after a Latin word ‘calx’, meaning burnt lime, which is an allusion to one of its important commercial uses.

Properties of Calcite

The following are the key properties of calcite:

  • Cell Data
    • Space group: R3c
    • a = 4.9896(2)
    • c = 17.0610(11)
    • Z = 6
  • Crystal Data
    • Hexagonal
    • Point group: 3 2/m
    • Well-formed crystals are common, {1011}, {2131}, thin to thick tabular {0001}, with combinations of over 1000 forms noted, to 7 m
    • Granular, stalactitic, in concretions, massive
    • Twinning: On {0112}, {1011}, {0001}, {0221} as twin and composition planes
    • X-ray powder pattern: 3.035 (100), 2.285 (18), 2.095 (18), 1.913 (17), 1.875 (17), 2.495 (14), 3.86 (12)
  • Chemical Composition
    Elements Content 1 Content 2
    CaO 53.60 56.03
    CO2 [44.22] 43.97
    MgO 1.74
    FeO 0.43 -
    Total [99.99] 100.00
  • Optical Properties
    • Optical class: Uniaxial (-); anomalously biaxial
    • Absorption: O > E
    • Dispersion: Very strong
    • ω = 1.658
    • ε = 1.486
    • 2V(meas.) = 0° to small
  • Estimated Properties
    Electron density Bulk density (electron density) = 2.71 g/cm3
    note: Specific gravity of calcite = 2.71 g/cm3
    Photoelectric PECalcite = 5.06 barns/electron
    U=PECalcite x ρ electron density= 13.70 barns/cm3
    Fermion index Fermion index = 0.0020908312
    Boson index = 0.9979091688
    Radioactivity
    Calcite is not radioactive

How to Identify Calcite

Calcite can be identified in the field by its color variations, such as white, pink, yellow, and brown. It is sometimes colorless. Its transparent to translucent to opaque form has {1011} perfect, {1011} perfect, and {1011} perfect cleavage. This mineral has a vitreous luster with a white streak. The fracture on this mineral is brittle - conchoidal. The density of calcite is 2.71 g/cm3, with a hardness of 3 – approximate to calcite. It is fluorescent and phosphorescent.

Global Distribution

Calcite is distributed in the following places:

  • Iceland - At the Helgustadanama mine, Reydarfjord
  • England - From Alston Moor, Egremont, and Frizington, Cumbria; Weardale, Durham; at Liskeard, Cornwall
  • Germany - From St. Andreasberg, Harz Mountains, and Freiberg, Saxony
  • Namibia - From Tsumeb
  • Congo - In the Mupine mine, Katanga Province
  • Romania - At Herja (Kisbanya), Baia Mare (Nagybanya) district
  • USA - From Rossie and Balmat, St. Lawrence Co. New York; at Hancock, Houghton Co. and in the Phoenix mine, Keeweenaw Co. Michigan; in Missouri, from many mines in Reynolds Co. and at Joplin, Jasper Co.; Galena, Cherokee Co. Kansas; and Picher, Ottawa Co. Oklahoma, in the Tri-State district; from the Elmwood mine, near Carthage, Smith Co. Tennessee; at Bisbee, Cochise Co. Arizona. In Mexico, from Santa Eulalia, and in Areponapuchic Canyon, Chihuahua; at many mines at Guanajuato; from Charcas, San Luis Potosi
  • Russia - At Dalnegorsk, Primorskiy Krai.

Occurrence of Calcite and Useful Mineral Association

Calcite occurs in major rock-forming minerals; in limestones, marbles, and chalks; a common cement in clastic sedimentary rocks; as gangue in hydrothermal veins; in alkalic to mafic igneous rocks; and commonly as speleothems in caves.

It is often associated with minerals such as dolomite, celestine, fluorite, barite, pyrite, marcasite, sphalerite, zeolites, talc, chalcedony, 'chlorite', tremolite, grossular, quartz, nepheline, diopside, orthoclase, and apatite.

References

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