Chamosite

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Chamosite
Chamosite-Klementite.jpg
General and classification
chemical formula (Fe 2+ , Mg, Fe 3+ ) 5 Al [(OH, O) 8 | AlSi 3 O 10 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.EC.55 ( 8th edition : VIII / H.23)
April 71, 2007
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic 2 / m
Space group C 2 / m
Lattice parameters a  = 5.373  Å ; b  = 9.306 Å; c  = 14.222 Å
β  = 97 ° 53 '
Formula units Z  = 2
Physical Properties
Mohs hardness 3
Density (g / cm 3 ) 3.0 to 3.4
Cleavage good after {001}
Break ; Tenacity uneven
colour gray-green, brown, black
Line color greenish gray
transparency translucent to opaque
shine Glass gloss, matt
Crystal optics
Refractive indices n α  = 1.600
n β  = 1.600
n γ  = 1.670
Birefringence δ = 0.070
Optical character biaxial negative

Chamosite (chamoisite) is a frequently occurring mineral from the mineral class of silicates and germanates. It crystallizes in the monoclinic crystal system with the chemical composition (Fe 2+ , Mg, Fe 3+ ) 5 Al [(OH, O) 8 | AlSi 3 O 10 ] and develops predominantly flaky, oolithic or massive mineral aggregates of gray, gray-green , brown or black color.

Etymology and history

Chamosit was first described in 1820 by Pierre Berthier , who named the mineral after its type locality Chamoson (municipality of the Conthey district in the French-speaking part of the canton of Valais, Switzerland).

classification

In the old (8th edition) and new classification of minerals by Strunz (9th edition) of Chamosite is part of the department of " phyllosilicates (phyllosilicates)". However, the 9th edition of Strunz's mineral system now subdivides it more precisely according to the structure of the silicate layers, whereby the mineral can be found in the subdivision of "layered silicates (phyllosilicates) with mica sheets, composed of tetrahedral or octahedral nets".

The systematics of minerals according to Dana also sorts the chamosite into the layered silicate department. In the Dana system, too , the crystal structure is further specified. However, the subdivision is described here as "layers of six-membered rings, alternating 1: 1, 2: 1 and octahedral".

Education and Locations

Chamosite is formed by metamorphosis or hydrothermal processes in iron-rich sediments and is then often found in the company of other iron-containing sediment minerals such as goethite , hematite , magnetite and siderite , but also calcite , kaolinite , olivine , plagioclase , pyrite , pyroxene and / or quartz .

So far, chamosite has been discovered at 265 sites (status: 2009), including in Bahariyya (Egypt); Constantine (Algeria); Biggend Shire / Queensland , Yancowinna County / New South Wales and Queenstown / Tasmania (Australia); the provinces of Liège and Luxembourg in Belgium; La Paz and Potosí departments in Bolivia; Minas Gerais and Pará in Brazil; Bulgaria ; Hebei , Hunan and Jiangxi in China; Baden-Württemberg (Black Forest), Bavaria , Saxony , Thuringia and other regions in Germany; Pays de la Loire in France; in Crete (Greece); England and Wales in Great Britain; some regions in Italy ; Honshū and Shikoku in Japan; New Brunswick , Ontario and Québec (Mont St.-Hilaire) in Canada; Cordoba in Colombia; Telemark and Vestfold in Norway; Hohe Tauern (Carinthia and Salzburg) in Austria; several regions in Russia and Slovakia ; Bern , Obwalden , Uri and Wallis in Switzerland; some regions of Spain ; Mpumalanga and the North Cape in South Africa; Bohemia and Moravia in the Czech Republic; as well as many regions in the US .

Samples of chamosite have also been taken on the sea floor of the Mid-Atlantic Ridge , more precisely the “Markov Depth” of the Sierra Leone rupture zone.

Chamosite is one of the minerals discovered on Mars, along with a few others.

Crystal structure

Chamosite crystallizes in the monoclinic crystal system in the space group C 2 / m with the lattice parameters a  = 5.373  Å ; b  = 9.306 Å, c  = 14.222 Å and β = 97 ° 53 'as well as two formula units per unit cell .

See also

Individual evidence

  1. ↑ Webmineral - Chamosite (English)
  2. ↑ a b c d Mineral data sheet - Chamosite (English; PDF file; 77 kB)
  3. ↑ a b Chamosite at mindat.org (engl.)
  4. ↑ Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 3-921656-17-6 .
  5. ↑ Martin Okrusch, Siegfried Matthes: Mineralogie: An introduction to special mineralogy, petrology and deposit science . 7th edition. Springer Verlag, Berlin, Heidelberg, New York 2005, ISBN 3-540-23812-3 , pp. 105, 301 ff .
  6. ↑ Mindat - Localities for Chamosite
  7. ↑ Edward A. Cloutis, Michael A. Craig et al. a .: Stability of hydrated minerals on Mars. In: Geophysical Research Letters. 34, 2007, S., doi : 10.1029 / 2007GL031267 .

literature

  • Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 257 .

Web links

Commons : Chamosite  - collection of images, videos and audio files