Malachite

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For other uses, see Malachite (disambiguation).
Malachite

Malachite specimen
General
Category Mineral
Chemical formula Cu2CO3(OH)2
Identification
Color Green
Crystal habit Massive, botryoidal, stalactitic
Crystal system Monoclinic - prismatic
Cleavage Perfect
Fracture Conchoidal to splintery
Mohs Scale hardness 3.5 - 4
Luster Dull/vitreous in large quantities, silky in crystal form
Streak green
Specific gravity 3.6 - 4

Malachite is a carbonate mineral normally known as "copper carbonate" with the formula Cu2CO3(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.

Contents

[edit] 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 associated with 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; Ural mountains, 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, often called King Solomon's Mines. 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.

[edit] Images

Malachite from the Democratic Republic of Congo

A polished slice of Malachite

Malachite

Malachite crystals atop blue azurite, with brown cuprite on the white kaolinite

Ball-and-stick model of malachite's unit cell

Polished Malachite

[edit] 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.

[edit] References

[edit] See also

Look up Malachite in
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