malachite
| malachite | |
|---|---|
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|
| General and classification | |
| other names |
|
| chemical formula | Cu 2 [(OH) 2 | CO 3 ] |
|
Mineral class (and possibly department) |
Carbonates and nitrates |
|
System no. to Strunz and to Dana |
5.BA.10 ( 8th edition : V / C.01) 16a.03.02.01 |
| Similar minerals | Azurite , chrysocolla |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | P 2 1 / a (No. 14, position 3) |
| Lattice parameters |
a = 9.50 Å ; b = 11.97 Å; c = 3.24 Å β = 98.7 ° |
| Formula units | Z = 4 |
| Twinning | mainly after (100) |
| Physical Properties | |
| Mohs hardness | 3.5 to 4 |
| Density (g / cm 3 ) | 3.6 to 4.05 |
| Cleavage | perfectly |
| Break ; Tenacity | shell-like, uneven, brittle |
| colour | pale to dark green |
| Line color | light green |
| transparency | translucent to opaque |
| shine | Diamond luster, glass luster, silk luster; matt, earthy |
| Crystal optics | |
| Refractive indices |
n α = 1.655 n β = 1.875 n γ = 1.909 |
| Birefringence | δ = 0.254 |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 43 °; calculated: 38 ° |
| Pleochroism | visible: almost colorless - yellowish green - deep green |
| Other properties | |
| Chemical behavior | soluble in acids and ammonia |
| Special features | noticeable, mostly wavy ligaments, pleochroism |
Malachite , also known as copper spar and mountain or copper green , is a common mineral from the mineral class of "carbonates and nitrates" with the chemical composition Cu 2 [(OH) 2 | CO 3 ]. From a chemical point of view, it is therefore a basic copper carbonate .
Malachite crystallizes in the monoclinic crystal system , but only very rarely develops crystals with needle-like to prismatic habit that are visible to the naked eye . It is mostly found in the form of massive or bunchy, banded aggregates in exclusively green color in all variations from pale to dark green.
Etymology and history
Pliny the Elder (23–79) already described malachite in his work Naturalis historia . The name derives from the Latin molochitis from the Greek word μαλάχη, in ancient Greek pronunciation maláchē for " mallow ". The color of the stone should be reminiscent of the strong green of the leaves.
The mineral was extremely popular in ancient Greece , ancient Egypt and the Roman Empire . The Egyptians, for example, carved all kinds of art objects such as amulets and scarabs from malachite and processed the finely ground mineral into expressive eye shadows . The fact that, contrary to earlier assumptions, malachite does not serve as the basis for the green color in wall paintings in ancient Egyptian burial chambers appears very likely based on recent research.
Malachite was also a popular mineral in ancient China . Remnants of the paint on the terracotta army in the Qin Shihuangdis mausoleum were identified as malachite pigment , and finely crafted malachite figures can be found in the Carnegie Museum of Natural History .
Malachite was widely used for soldering goldsmith work until the Middle Ages . It was ground to dust and processed into an emulsion with the help of isinglass and water , the so-called "gold glue" (Greek chrysokolla; chrysos: gold, kolla: glue; see also chrysocolla ). In a charcoal fire the gold glue can be reduced to copper by the carbon monoxide present , creating a solderable copper alloy . This made it possible to solder fine wires and gold balls onto a surface. The Etruscans were masters in using this method, and the ancient Egyptians also knew this method. An example of the use by the Egyptians are the death mask and other objects from the tomb of the pharaoh Tutankhamun .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral systematics according to Strunz , malachite still belonged to the common mineral class of "carbonates, nitrates and borates " and there to the department of "anhydrous carbonates with foreign anions", where together with the namesake Minerals azurite and rosasite as well as the other members aurichalcite , brianyoungite , georgeit , glaucomaite , kolwezite , losyite , mcguinnessite , nullaginite , pokrovskite , sclarite and zinc rosasite form the "azurite-rosasite series".
Since the complete revision of Strunz's mineral systematics in the 9th edition (2001), the mineral class of carbonates (and relatives) has been redistributed and the borates form a class of their own. The malachite is therefore now in the mineral class of "carbonates and nitrates" and there in the department of "carbonates with additional anions; without finding H 2 O ”. However, this is now more precisely subdivided according to the cations involved and the mineral sorted according to its composition in the sub-section “With Cu, Co, Ni, Zn, Mg, Mn”, where the “malachite group” with the system no. 5.BA.10 and the other members Chukanovit , Georgeit, Glaukosphärit, Kolwezit, Mcguinnessit, Nullaginit, Pokrovskit, Rosasit and Zinc rosasite.
In the systematics of minerals according to Dana , which is mainly used in the English-speaking world , the carbonates, nitrates and borates form a common mineral class as in the outdated Strunz system. The malachite can be found there in the section of “ carbonates with hydroxyl or halogen and the general formula (AB) 2 (XO) 3 Zq ”, where the “malachite group” with system no. 16a.03.01 and the other members Nullaginit, Pokrovskit and Chukanovit.
Crystal structure
Malachite crystallizes monoclinically in the space group P 2 1 / a (space group no. 14, position 3) with the lattice parameters a = 9.50 Å ; b = 11.97 Å; c = 3.24 Å and β = 98.7 ° and 4 formula units per unit cell .
properties
Malachite is characterized by its exclusively green color, which occurs in banded layers between light green and black green. Malachite generally shows a very strong pleochroism (multicolor), which, depending on the direction of the incidence of light, manifests itself in a color change from almost colorless to yellow-green to deep green.
The Mohs hardness of the mineral is about 3.5 to 4 and its density 3.6 to 4.05 g / cm³, depending on the purity of the compound. Its copper content is around 57 percent.
Because of its low hardness and its not particularly high density, malachite tends to break. Sun exposure makes it pale, water can take its shine away and in some cases also cause a color change.
Education and Locations
Malachite is a typical secondary mineral that as weathering product in the oxidation zone of copper - deposits forming. There it occurs mainly in close paragenesis with azurite , from which it arises through water absorption, but can also be associated with many other minerals, such as barite , bornite , calcite , cerussite , chrysocolla , cuprite , dolomite , goethite , linarite and others Quartz . Malachite can also be a component of copper pechers and limonite .
So far (as of 2010) malachite has been detected at almost 8800 sites worldwide, including in Afghanistan , Egypt , 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 , on the Fiji Islands , in Finland , France , Greece , Greenland , Guatemala , India , Indonesia , Iran , Ireland , on the Isle of Man , in Israel , Italy , Jamaica , Japan , on the Jordan , on the Virgin Islands , in Cambodia , Canada , Kazakhstan , Kyrgyzstan , Colombia , on Cuba , Laos , Luxembourg , on Madagascar , in Malaysia , Morocco , Mexico , Mongolia , Namibia , the Netherlands , New Caledonia , New Zealand , North Macedonia , Norway , Austria , Pakistan , Panama , Papua New Guinea , Paraguay , Peru , the Philippines , Poland , Portugal , rum Austria , Russia , the Solomon Islands , Zambia , Sweden , Switzerland , Serbia , Zimbabwe , Slovakia , Slovenia , Spain , South Africa , South Korea , Swaziland , Tajikistan , Taiwan , Thailand , the Czech Republic , Tunisia , Turkey , Turkmenistan , Ukraine , Hungary , Uzbekistan , the United Kingdom (Great Britain), the United States of America (USA) and Vietnam .
use
As a gem
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Malachite is mainly used as a gem in the arts and crafts. In the Kremlin in Moscow , entire columns are made of malachite, which comes from the Urals . The banding in various shades of green, which is similar to a wood grain, is particularly beautiful and rated accordingly. Due to its toxic dust and grinding water, however, it is complex to process and therefore expensive.
It is relatively easy, albeit time-consuming, to provide the calcium carbonate-containing shells of mussels and snails , but also marble objects with a coating of malachite for decorative purposes. After a few weeks of storage in concentrated, aqueous copper sulphate solution, a more or less thick layer of malachite forms on the surface with the development of carbon dioxide (CO 2 ). The shell limestone is gradually dissolved.
As a pigment
Finely ground malachite has been used as a pigment called “cold green” for wall paintings since ancient times.
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In a similar way to malachite coatings on shellfish, the mineral color malachite green can be produced from marble powder by mixing it with copper sulphate. The fineness of the powder determines the quality of the resulting pigment , which is mainly used in oil painting . A famous example of the use of malachite in painting is the green curtain in the background of the Sistine Madonna by Raphael .
An organic dye of the same color called malachite green is not extracted from the mineral malachite.
Manipulations and imitations
Since malachite is a coveted, but also quite soft (hardness 3.5 to 4 compared to glass 5 to 5.5), more porous and its perfect cleavability due to sensitive gemstones, rough stones are stabilized by adding a mixture of malachite dust and synthetic resin . With the same treatment method, however, larger, usable malachites are reconstructed from small fragments . In drum stones and " Donuts " these methods of manipulation are common and in the conversion phase azurite observed -Malachit often. Stabilized and reconstructed stones can be recognized by their grainy, mottled appearance due to the filling of the gaps with filler. Malachite is often imitated by colored jasper , agate or marble . The "red malachite" (trade name) is actually red jasper. Malachite occurs naturally only in green shades.
Malachite is now also produced synthetically .
Precautions
As a copper mineral, malachite also has toxic properties. Water with a malachite in it should therefore never be drunk. It is just as dangerous to saw or crush a malachite without suitable protective measures (dust mask, vacuum cleaner), since the fine dust releases considerable amounts of soluble copper and is accordingly toxic.
To reduce dents, cracks and color changes, the mineral should be handled with care. Storage in the dark is excessive, but direct, prolonged exposure to sunlight can cause visible fading. Even brief contact with water is by no means bad. However, a long-lasting bath usually removes the shine from the stone.
Esoteric
Malachite is assigned to the Capricorn as the “planet stone ” of Venus , as the “ zodiac stone” next to the main stones onyx and cat-eye quartz and to Friday as a weekday stone next to the emerald .
Malachite is used by esotericists as a healing stone against various ailments such as headaches, eye infections, arthritis and irritation of the sciatic nerve . There is no scientific evidence of this.
See also
literature
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 578 (first edition: 1891).
- Petr Korbel, Milan Novák: Mineral Encyclopedia (= Villager Nature ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 122 .
- Stefan Muntwyler: Malachite. Hotly contested raw material copper . In: color pigments, dyes, color stories. Bolognese chalk, Rügen chalk, champagne chalk, Carrara marble. = Peach stone black, grape stone black, cherry stone black, flame soot . 2nd, revised edition. Alata, Winterthur 2011, ISBN 978-3-03302968-2 , p. 160-167 .
- Malachite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 66 kB ; accessed on July 24, 2017]).
Web links
- Mineralienatlas: Malachit und Mineralienatlas: Mineralienportrait / Malachit (Wiki); long loading time - very extensive
- Kremer pigments - malachite
- Malachite , ColourLex
Individual evidence
- ↑ a b c Malachite, mountain or copper green, copper spar at Zeno.org, p. 286
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 294 .
- ↑ Webmineral - Malachite (English)
- ↑ a b c d e f Mindat - Malachite (English)
- ↑ China internal - malachite
- ↑ a b Bernhard Bruder: Decorated stones. Recognizing imitations and manipulations in gemstones and minerals . Neue Erde Verlag, Saarbrücken 2005, ISBN 3-89060-079-4 , p. 79-80 .
- ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 192 .
- ↑ List of localities for malachite in the Mineralienatlas and Mindat
- ^ Karl Heinz Weber: The Sistine Madonna. In: Maltechnik, Restauro. Vol. 90, No. 4, 1984, ISSN 0025-1445 , pp. 9-28
- ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 284-286 .
- ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 290 .