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Home » Minerals » Malachite

Malachite

Used as an ore of copper, a pigment and a gemstone for thousands of years.



What is Malachite?



Malachite is a green copper carbonate hydroxide mineral with a chemical composition of Cu2(CO3)(OH)2. It has been used as a gemstone and sculptural material for thousands of years and is still popular today. The green color of malachite is enduring and powdered malachite was used as a pigment and coloring agent for thousands of years. Malachite was one of the first ores used to produce copper metal but it is of minor importance today.


Where Does Malachite Form?



Malachite is a mineral that forms at shallow depths within the Earth, in the oxidizing zone above copper deposits. There it precipitates from solution in fractures, caverns, and the intergranular spaces of porous rock. It often forms within limestone where a subsurface chemical environment favorable for the formation of carbonate minerals can occur. Associated minerals include: azurite, bornite, calcite, chalcopyrite, copper, cuprite, and a variety of iron oxides.

Some of the first malachite deposits to be exploited were located in Egypt and Israel. Over 4000 years ago they were mined and used to produce copper. Material from these deposits was also used to produce gemstones, sculptures and pigments. Several large deposits in the Ural Mountains of Russia were aggressively mined and supplied abundant gem and sculptural material in the 1800s. Very little is produced from these deposits today. Much of the malachite entering the lapidary market today is from deposits in the Democratic Republic of the Congo. Smaller amounts are produced in Australia, France and Arizona.


Physical Properties of Malachite



Malachite's most striking physical property is its green color. All specimens of the mineral are green and range from a pastel green, to a bright green, to an extremely dark green that is almost black. It is typically found in as stalactites and botryoidal coatings on the surfaces of subsurface cavities - similar to the deposits of calcite found in caves. When these materials are cut into slabs and pieces the sawn surfaces often exhibit banding and eyes that are similar to agate.

Physical Properties of Malachite

Chemical Classification carbonate
Color green
Streak green
Luster rare crystals are vitreous to adamantine, fibrous specimens are silky, massive specimens are dull to earthy
Diaphaneity most specimens are opaque, crystals are translucent
Cleavage perfect in one direction, fair in a second direction
Mohs Hardness 3.5 to 4.0
Specific Gravity 3.6 to 4.0
Diagnostic Properties green color, soft, efferveses with dilute HCl to produce a green liquid
Chemical Composition Cu2(CO3)(OH)2
Crystal System monoclinic
Uses a minor ore of copper, gemstones, small sculptures, pigment


Malachite is rarely found as a crystal, but when found the crystals are usually acicular to tabular in shape. The crystals are bright green in color, translucent, with a vitreous to adamantine luster. Noncrystalline specimens are opaque, usually with a dull to earthy luster.

A high copper content gives malachite a high specific gravity that ranges from 3.6 to 4.0. This property is so striking for a green mineral that it makes malachite easy to identify. Malachite is one of a small number of green minerals that produce effervescence in contact with dilute hydrochloric acid. It is also a soft mineral with a Mohs hardness of 3.5 to 4.0.


Malachite as a Gem Material



The vivid green color, bright polished luster, banding and eyes of malachite make it very popular as a gemstone. It is cut into cabochons, used to produce beads, sliced into inlay material, sculpted into ornamental objects and used to manufacture tumbled stones. Small boxes made from slices of malachite are attractive and popular.

Some of the most spectacular gem-quality malachite involves intergrowths, inclusions and admixtures of malachite with other copper minerals such as azurite (azurmalachite) or azurite, chrysocolla, turquoise and pseudomalachite (eliat stone).

Malachite's use as gem and ornamental stone is limited by its properties. It has perfect cleavage and a Mohs hardness of 3.5 to 4. These limit its use to items that will not suffer abrasion and impact. It is also sensitive to heat and reacts with weak acids. These properties further limit its use and require care during cleaning, repair and maintenance. Malachite is sometimes treated with wax to fill small voids and improve its luster.

Synthetic malachite has been produced and used to make jewelry and small sculptures. Poorly done synthetics are often recognized by their unnatural color. The better synthetics can usually be recognized because their banding and eyes do not have a natural geometry. An experienced person can identify most of the synthetic and imitation materials on sight.


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malachite gemstone
A malachite cabochon (30x40 millimeter) cut from material mined in the Democratic Republic of the Congo. This photo shows the agate-like banding in various hues of green that is typical of malachite.


botryoidal malachite
Close-up of botryoidal malachite in a sea foam green color from Bisbee, Arizona. This view spans an area of the specimen about 5 millimeters wide and high. Specimen and photo by Arkenstone / www.iRocks.com.


stalactitic malachite
A specimen of stalactitic malachite from the Kasompi Mine, Democratic Republic of the Congo. The specimen is approximately 21 x 16 x 12 centimeters in size. Specimen and photo by Arkenstone / www.iRocks.com.


malachite banding and eyes
Two views of a specimen of botryoidal malachite - one external and one internal polished surface. This photo pair shows how agate-like bands and eyes of malachite occur beneath a botryoidal structure. This specimen was collected near Katanga, Democratic Republic of Congo. Photograph by Didier Descouens. Used here under a Creative Commons License.


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