Malachite

Malachite is a commonly occurring mineral from the mineral class of carbonates. It crystallizes in the monoclinic crystal system with the chemical composition Cu2 [( OH) 2 | CO 3 ] and usually develops moderate or racemose, banded aggregates, rarely acicular, prismatic crystals in only green color in all variations from pale to dark green.

Special Features

Characteristic of malachite is his only green color that occurs in banded layers between light green to black green. Malachite generally shows a very strong pleochroism ( multi-color ), which manifests itself as a change in color from almost colorless to yellow-green to deep green depending on the direction of light incidence.

The Mohs hardness of the mineral is about 3.5 and 4 and the density from 3.6 to 4.05 g / cc, depending on the purity of the compound. Its copper content is about 57 percent.

Because of its low hardness and its not particularly high density of malachite tends to break it. Sunlight makes him pale, water can take it the shine and in some cases also have a color change result.

Etymology and history

Already Pliny the Elder ( 23-79 AD ) described the malachite in his work Naturalis historia. The name derives, via Latin molochitis well μαλάχη from the Greek word in ancient Greek pronunciation malache for " mallow " from. The color of the stone is a reminder of the vibrant green of the leaves.

Already in Ancient Greece, Ancient Egypt and the Roman Empire, the mineral was exceedingly popular. The Egyptians carved from malachite, for example, all kinds of art objects such as amulets and scarabs and processed the finely ground mineral to expressive eye shadow. That malachite, contrary to earlier assumptions does not serve as the basis of the green color in wall paintings in ancient Egyptian grave chambers, appears most likely due to recent research.

Also in Chinese antiquity was a popular mineral malachite. So remnants of color coatings were identified on the Terracotta Army in the Mausoleum of Qin Shihuangdis as malachite pigment and the Carnegie Museum of Natural History include finely crafted malachite figures to find.

Malachite was widely used until the Middle Ages for the soldering of gold work. There was ground to powder, and processed with the aid of fish glue and water to form an emulsion, the so -called " Goldleim " (Greek chrysokolla; chrysos: Gold, kolla: glue; see also chrysocolla ). In a charcoal fire of Goldleim can be reduced by the carbon monoxide present to copper, with a solderable copper alloy. Thus it was possible to solder fine wires and gold beads on a surface. The Etruscans were masters in the use of this procedure as well as the ancient Egyptians knew this method. An example of the application by the Egyptians are the death mask and other items from the grave of Pharaoh Tutankhamun.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the malachite still belonged to the common mineral class of " carbonates, nitrates and borates " and then to the Department of " water clear carbonates with foreign anions ", where he, together with the eponymous minerals azurite and Rosasit as well as the other members Aurichalcit, Brianyoungit, Georgeit, Glaukosphärit, Kolwezit, Loseyit, McGuinnessit, Nullaginit, Pokrovskit, Sclarit and Zinkrosasit the " Azurite- Rosasit series" forms.

Since the full review of the Strunz'schen Mineral classification in the 9th edition (2001) the mineral class of carbonates ( and relatives ) is redistributed and the borates form a separate class. Malachite is therefore now in the mineral class of " carbonates and nitrates " and find it there in the department of " Carbonates with additional anions, without H2O". However, this is now a more specific breakdown of the individual involved cations and the mineral according to its composition in the subsection "With Cu, Co, Ni, Zn, Mg, Mn" sorted, where he served as the eponymous mineral the " Malachitgruppe " with the system no. Forms 5.BA.10 and the other members Chukanovit, Georgeit, Glaukosphärit, Kolwezit, Mcguinnessit, Nullaginit, Pokrovskit, Rosasit and Zinkrosasit.

In the mostly commonly used in the English-speaking classification of minerals according to Dana, the carbonates, nitrates and borates form a common mineral class as in the outdated Strunz'schen systematics. Malachite is there, however, in the department of " carbonates with hydroxyl or halogen, and the general formula ( AB) 2 (XO) 3Zq " to find where he was the eponymous mineral " Malachitgruppe " with the system no. Forms 16a.03.01 and the other members Nullaginit, Pokrovskit and Chukanovit.

Education and Locations

Malachite is a typical secondary mineral that forms as a weathering product in the oxidation zone of copper deposits. It occurs there, especially in close paragenesis with Azurite on, from which it is produced by absorption of water, but can be associated with many other minerals, such as, among others, barite, bornite, calcite, cerussite, chrysocolla, cuprite, dolomite, goethite, Linarit and quartz. Malachite can also be part of Kupferpecherz and limonite.

Worldwide, malachite so far (as of 2010) are detected at almost 8800 localities, so include Afghanistan, Algeria, Angola, Antarctica, Argentina, Armenia, Aruba, Australia, Azerbaijan, Belgium, Bolivia, Bosnia and Herzegovina, Brazil, Bulgaria, Chile, China, Costa Rica, Democratic Republic of the Congo, Germany, Dominican Republic, Ecuador, in the Fiji Islands, Finland, France, Greece, Greenland, Guatemala, India, Indonesia, Iran, Ireland, the Isle of Man, in Israel, Italy, Jamaica, Japan, at the Jordan, in the Virgin Islands, Cambodia, Canada, Kazakhstan, Kyrgyzstan, Colombia, Cuba, Laos, Luxembourg, Madagascar, Malaysia, Morocco, Macedonia, Mexico, Mongolia, Namibia, the Netherlands, New Caledonia, New Zealand, Norway, Austria, Pakistan, Panama, Papua New Guinea, Paraguay, Peru, Philippines, Poland, Portugal, Romania, Russia, the Solomon Islands, Zambia, Sweden, Switzerland, Serbia, Zimbabwe, Slovakia, Slovenia, Spain, South Africa, South Korea, Swaziland, Tajikistan, Taiwan, Thailand, Tunisia, Turkey, Turkmenistan, Ukraine, Uzbekistan, the United Kingdom ( UK), the United States of America (USA ) and Vietnam.

Crystal structure

Malachite crystallizes in the monoclinic space group P21 / a with lattice parameters a = 9.50 Å; b = 11.97 Å; c = 3.24 Å and 98.7 ° β = 4 and formula units per unit cell.

Use

As a gemstone

Malachite is mainly used as a gemstone in arts and crafts. In the Kremlin in Moscow entire columns of malachite are made, who is from the Urals. Particularly beautiful and valued in accordance with the occurring in various shades of green banding, similar to a wood grain visible. Because of its toxic dust and abrasive water but it is complicated and correspondingly expensive to process.

Relatively easy, though time consuming, can be the case of calcium carbonate shells and snails, but also provided items from marble to jewelry purposes with a coating of malachite. After a few weeks of storage in concentrated aqueous solution of copper sulfate forms on the surface with the evolution of carbon dioxide ( CO2), a more or less thick layer of malachite. The shell is thereby gradually dissolved.

As a pigment

Malachite is a finely ground since antiquity as a pigment called " Cold Green " for murals in use.

In a manner similar Malachitüberzüge in crustaceans, also the mineral malachite green color can be produced from marble powder by mixing it with copper sulfate. The fineness of the powder determines the quality of the resulting pigment is mainly used in oil painting.

Manipulation and imitation

Since malachite a popular, but also very soft (hardness 3.5 to 4 over glass 5 to 5.5 ) is porous and its perfect cleavage because sensitive gemstone, rough stones are stabilized by introducing a Malachitstaub resin mixture. With the same treatment but larger, use enabled Malachite also be reconstructed from small fragments. With stones and drum " donuts " of manipulation of these methods are widely used and azurite, malachite observed in the conversion phase of times. Visible are stabilized and reconstructed stones at their grain - mottled appearance due to the filling of the gaps with putty. Often imitated Malachite is also dyed jasper, agate or marble. The " Red Malachite " (trade name) is actually red jasper. Malachite is found in nature only in green hues.

Meanwhile Malachite is also produced synthetically.

Precautions

The copper mineral malachite also has toxic properties. Water in which a malachite has located, should therefore never be drunk. Also dangerous is the sawing and grinding of a malachite without appropriate protective measures (dust mask, vacuum cleaner ), as the fine dust releases considerable amounts of soluble copper and is correspondingly toxic.

To reduce dents, cracks and discoloration, the mineral should be treated with caution. Storage in the dark, although exaggerated, but a direct, prolonged sunlight can cause a visible fading. Also, the short contact with water is by no means bad. However, a long-lasting bathroom takes the stone usually gloss.

Esoteric

In the esotericism of malachite is associated with the planet Venus and the element earth. He should know how to heal as a healing stone all kinds of gynecological problems and because of his rumored property to ease labor pains, also called " midwives stone ". But it should also make alert to the language of animals. Scientific thereof is not occupied.