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Malachite

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Malachite is a carbonate mineral with chemical composition of Cu2CO3(OH)2. Possibly the earliest ore of copper, malachite is believed to have been mined in the Sinai and eastern deserts of ancient Egypt from as early as 3000 BCE. Single crystals are uncommon; when found, they are short to long prisms. Malachite is usually found as botryoidal or encrusting masses, often with a radiating fibrous structure and banded in various shades of green. It also occurs as delicate fibrous aggregates and as concentrically banded stalactites. Malachite occurs in the altered zones of copper deposits, where it is usually accompanied by lesser amounts of azurite. It is primarily valued as an ornamental material and gemstone. Single masses that weighed up to 51 tons were found in the Ural Mountains of Russia in the 19th century

Name: Derived from the Greek word for mallows, in allusion to its green color.

Crystallography: Monoclinic; prismatic. Crystals usually slender prismatic but seldom distinct. Crystals may be pseudomorphous after azurite. Usually in radiating fibers forming botryoidal or stalactitic masses. Often granular or earthy.

Composition: Basic carbonate of copper, Cu2C03(0H)2. CuO = 71.9 percent, C02 = 19.9 percent, H20 = 8.2 percent. Cu = 57.4 percent

Diagnostic Features: Recognized by its bright green color and botryoidal forms, and distinguished from other green copper minerals by its effervescence in acid

Chemical Properties of Malachite

Chemical Classification Carbonate mineral
Chemical Composition Cu2CO3(OH)2

Physical Properties of Malachite

Color Bright green, dark green, blackish green, commonly banded in masses; green to yellowish green in transmitted light
Streak Light green
Luster Adamantine to vitreous; silky if fibrous; dull to earthy if massive
Cleavage Perfect on {201}, fair on {010}.
Diaphaneity Translucent to opaque
Mohs Hardness 3.5–4.0
Specific Gravity 3.6–4
Diagnostic Properties Green color, soft, effervesces with dilute HCl to produce a green liquid.
Crystal System Monoclinic
Tenacity Brittle
Fracture Irregular/Uneven, Sub-Conchoidal, Fibrous
Density 3.6 – 4.05 g/cm3 (Measured)    4 g/cm3 (Calculated)

Optical Properties of Malachite

Type Anisotropic
Color / Pleochroism Visible
Twinning Common as contact or penetration twins on {100} and {201}. Polysynthetic twinning also present.
Optic Sign Biaxial (-)
Birefringence δ = 0.254
Relief Very High

Occurrence

Malachite is an important and widely distributed copper ore of secondary origin. Found in the oxidized portions of copper veins associated with azurite, cuprite, native copper, iron oxides, and the various sulfides of copper and iron. Usually occurs in copper veins that lie in limestone

Uses Area

  • When discovered in large pieces, the banded variety of Malachite makes a treasured decorative stone.   
  • Small ornamental gadgets, which includes containers and animal figures, are carved out of this compact stone, and if nicely polished, they may be treasured.
  • Malachite is likewise used as a minor gemstone, and is cut into cabochons and original into necklace beads. “Azure-malachite” is also used as gemstone and has the equal gem applications as banded Malachite.
  • Malachite could be very famous among mineral creditors, specifically curiously fashioned and banded specimens. It is also used as an ore of copper and beaten to make a green pigment.

Association: Azurite, cuprite, cerussite, chrysocolla, calcite. “limonite”.

Distribution

Many localities; some for abundant and rich material include:

  • from Chessy, near Lyon, Rhone, France.
  • In Russia, large pure masses formerly from mines around Nizhni Tagil and Ekatarinburg, Ural Mountains.
  • In Congo, in Katanga Province (Shaba Province, Zaire), from Lubumbashi, at the Musonoi mine, near Kolwezi, and elsewhere, with large crystals from the Mashamba West mine.
  • In Namibia, from Tsumeb, and as large crystals at the Onganja mine, 60 km northeast of Windhoek.
  • In Australia, from Broken Hill and Cobar, New South Wales, and Burra, South Australia.
  • In the USA, from the Copper Queen, Czar, and other mines in the Warren district, Bisbee, Cochise Co. and at Morenci, Greenlee Co., Arizona; in the Fierro-Hanover district and at Santa Rita, Grant Co., New Mexico.

References

  • Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
  • Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
  • Mindat.org. (2019). Malachite: Mineral information, data and localities.. [online] Available at: https://www.mindat.org/min-727.html [Accessed 4 Mar. 2019].
Cite this article as: Geology Science. (2019). Malachite. [online] Available at: http://geologyscience.com/minerals/malachite/ [9th December 2019 ]
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