Malachite: Difference between revisions
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'''Malachite''' is a [[ |
'''Malachite''' is a [[ball sack]] normally known as "copper carbonate" with the [[chemical formula|formula]] [[copper|Cu]][[carbonate|CO<sub>3</sub>]].[[copper|Cu]][[hydroxide|(OH)]]<sub>2</sub>. This green-colored mineral crystallizes in the [[monoclinic]] crystal system, and most often forms [[botryoidal]], fibrous, or [[stalagmite|stalagmitic]] masses. Individual crystals are rare but do occur as slender to acicular prisms. [[Pseudomorph]]s after more tabular or blocky azurite crystals also occur. <!--unintelligable--> |
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==Etymology and history== |
==Etymology and history== |
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Revision as of 12:15, 5 May 2009
| Malachite | |
|---|---|
 Malachite specimen | |
| General | |
| Category | Carbonate mineral |
| Formula (repeating unit) | CuCO3.Cu(OH)2 |
| Crystal system | Monoclinic - prismatic |
| Identification | |
| Color | Bright green to blackish green |
| Crystal habit | Massive, botryoidal, stalactitic |
| Cleavage | Perfect on [201] fair on [010] |
| Fracture | Conchoidal to splintery |
| Mohs scale hardness | 3.5 - 4.0 |
| Luster | Dull/vitreous in large quantities, silky in crystal form |
| Streak | light green |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.6 - 4 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.655 nβ = 1.875 nγ = 1.909 |
| Birefringence | δ = 0.254 |
| References | [1][2] |
Malachite is a ball sack normally known as "copper carbonate" with the formula CuCO3.Cu(OH)2. This green-colored mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses. Individual crystals are rare but do occur as slender to acicular prisms. Pseudomorphs after more tabular or blocky azurite crystals also occur.
Etymology and history
The stone's name derives (via Latin and French) from Greek molochitis, "mallow-green stone", from molochē, variant of malachē, "mallow". Malachite was used as a mineral pigment in green paints from antiquity until about 1800. The pigment is moderately lightfast, very sensitive to acids and varying in color. The natural form was being replaced by its synthetic form, verditer amongst other synthetic greens. It is also used for decorative purposes, such as in the Malachite Room in the Hermitage, which features a large malachite vase (unknown scale). "The Tazza", one of the largest pieces of malachite in North America and a gift from Tsar Nicholas II, stands as the focal point in the center of the room of Linda Hall Library.
Occurrence and historical uses
Malachite often results from weathering of copper ores and is often found together with azurite (Cu3(CO3)2(OH)2), goethite, and calcite. Except for its vibrant green color, the properties of malachite are similar to those of azurite and aggregates of the two minerals occur frequently together. Malachite is more common than azurite and is typically associated with copper deposits around limestones, the source of the carbonate.
Large quantities of malachite have been mined in the Urals. It is found in the Democratic Republic of Congo; Zambia; Tsumeb; Namibia; Russia; Mexico; Broken Hill, New South Wales; England; Lyon; and in the Southwestern United States especially in Arkansas and Arizona. In Israel, malachite is extensively mined at Timna valley, often called King Solomon's Mines although research has shown that the site was not in use during the 10th century.[3]. Archeological evidence indicates that the mineral has been mined and smelted at the site for over 3,000 years. Most of Timna's current production is also smelted, but the finest pieces are worked into silver jewelry.
In Greek mythology, the throne of Demeter, goddess of grain and harvest, was fashioned from malachite and adorned with golden pigs and ears of barley.[4]
Gallery
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Malachite from the Democratic Republic of Congo -
A polished slice of Malachite -
Malachite -
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Ball-and-stick model of malachite's unit cell -
Polished Malachite
References
- ^ http://webmineral.com/data/Malachite.shtml Webmineral data
- ^ http://mindat.org/min-2550.html Mindat
- ^ Parr, Peter J review of "Timma: Valley of the Biblical Copper Mines" by Beno Rothenberg Bulletin of the School of Oriental and African Studies, University of London, Vol. 37, No. 1, In Memory of W. H. Whiteley (1974), pp. 223-224
- ^ http://alex.edfac.usyd.edu.au/BLP/websites/ROBMATULEWICZ/gods.html The Palace of Olympus (University of Sydney, Australia)
- Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York ISBN 0-471-80580-7
- Mineral Galleries
- Virtual tour of the Malachite Room
See also
