malachite, a mineral, the green basic carbonate of copper occurring in crystals of the monoclinic system or (more usually) in masses. It is translucent or opaque; the luster is silky, vitreous, adamantine, or dull. It takes a good polish. An important ore of copper, it also serves as a gem and for various ornamental purposes and, when finely ground, as a pigment. It is found associated with other ores of copper (especially azurite) in various parts of the United States and in Chile, Russia, Congo (Kinshasa), Zimbabwe, and Australia.

Widespread carbonate mineral of copper, a hydrous copper carbonate, Cu₂CO₃(OH)₂. Because of its distinctive, bright green colour and its presence in the weathered zone of nearly all copper deposits, malachite serves as a prospecting guide. It is found in Siberia, France, Namibia, and Arizona. Malachite has been used as an ornamental stone and as a gemstone.

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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.

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; 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.

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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 New hermitage interior.jpg. "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.

References

• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York ISBN 0-471-80580-7
• Mineral Galleries
• Webmineral data
• Mindat
• Virtual tour of the Malachite Room

See also

• aventurine
• dioptase