Copiapit

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Copiapit
Copiapite-692700.jpg
Copiapit (yellow) from the Antler Mine, Arrastra Mountain, Hualapai District, Mohave County , Arizona, USA (field of view approx. 9 mm)
General and classification
other names
  • Basic sulfuric acid iron oxide
chemical formula Fe 2+ Fe 3+ 4 [(OH) 2 | (SO 4 ) 6 ] • 20H 2 O
Mineral class
(and possibly department) 		Sulphates (selenates, tellurates, chromates, molybdates and tungstates) - sulphates containing water with foreign anions
System no. to Strunz
and to Dana 		7.DB.35 ( 8th edition : VI / D.10)
10/31/05/01
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Space group P 1 (No. 2)Template: room group / 2
Lattice parameters a  = 7.39  Å ; b  = 18.21 Å; c  = 7.29 Å
α  = 93.7 °; β  = 102.0 °; γ  = 99.3 °
Formula units Z  = 1
Twinning Contact twins, twin axis [ 1 01]
Physical Properties
Mohs hardness 2.5 to 3
Density (g / cm 3 ) measured: 2.04 to 2.17; calculated: [2.12]
Cleavage perfect after {010}, imperfect after { 1 01}
colour light to dark yellow, yellow-orange; yellow-green to olive-green in dense aggregates
Line color light yellow
transparency transparent to translucent
shine Pearlescent
Crystal optics
Refractive indices n α  = 1.506 to 1.540
n β  = 1.528 to 1.549
n γ  = 1.575 to 1.600
Birefringence δ = 0.069
Optical character biaxial positive
Axis angle 2V = 45 ° to 74 ° (measured), 48 ° to 72 ° (calculated)
Pleochroism X = Y = light yellow to colorless; Z = sulfur yellow
Other properties
Chemical behavior soluble in water

Copiapit is a relatively rare mineral from the mineral class of "sulphates (selenates, tellurates, chromates, molybdates and tungstates)" with the chemical formula Fe 2+ Fe 3+ 4 [(OH) 2 | (SO 4 ) 6 ] · 20H 2 O and chemical point of view so that a hydrous iron - sulfate with additional hydroxide . Copiapit is the most common ferric sulfate.

Copiapit crystallizes in the triclinic crystal system , but develops only millimeter-sized crystals with a thin tabular habit and a mother-of-pearl-like sheen on the table surfaces. It is mostly found in the form of crusty coatings as well as flaky or granular to powdery mineral aggregates . Depending on the characteristics, the mineral is transparent to opaque and light to dark yellow or yellow-orange in color. In dense aggregates, however, copiapite can also appear yellow-green to olive-green. His line color , on the other hand, is always light yellow.

With a Mohs hardness of 2.5 to 3, copiapite is one of the soft to medium-hard minerals that are slightly easier to scratch with a copper coin than the reference mineral calcite .

Etymology and history

Copiapit was first discovered in the province of Copiapó near the city ​​of the same name in the Chilean Región de Atacama .

Copiapit was scientifically described in 1833 by Heinrich Rose under the name of alkaline sulfuric iron oxide . Wilhelm von Haidinger named the mineral in 1845 after its type of locality .

The type material of the mineral is at Harvard University in Cambridge , Massachusetts (USA) under the catalog no. 99059 kept.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the copiapit belonged to the mineral class of "sulfates, chromates, molybdates, tungstates" (including selenates and tellurates) and there to the department of "water-containing sulfates with foreign anions ", where, together with Botryogen, he established the "Botryogen Copiapit Group" with the system no. VI / D.10 and the other members Aluminocopiapit , Calciocopiapit , Chaidamuit , Cuprocopiapit , Ferricopiapit , Guildit , Magnesiocopiapit , Zincbotryogen and Zincocopiapit formed.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns the copiapit to the category of "Sulphates (selenates, etc.) with additional anions, with H 2 O". However, this is further subdivided according to the relative size of the cations involved and the crystal structure , so that the mineral is classified in the sub-section “with medium-sized cations; isolated octahedron and limited units "can be found, where the" Copiapitgruppe "with the system no. 7.DB.35 and the other members Aluminocopiapit, Calciocopiapit, Cuprocopiapit, Ferricopiapit , Magnesiocopiapit and Zincocopiapit.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the copiapit to the class of "sulfates (and relatives)" and there in the department of "water-containing sulfates with hydroxyl or halogen". Here he is also the namesake of the " Copiapit Group " with the system no. October 31, 2005 to be found in the subsection “Various hydrous sulphates with hydroxyl or halogen”.

Crystal structure

Copiapit crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a  = 7.39  Å ; b  = 18.21 Å; c  = 7.29 Å; α = 93.7 °; β = 102.0 ° and γ = 99.3 ° and one formula unit per unit cell . Template: room group / 2

The crystal structure of Copiapit is along [101] complex of chains metal coordination - octahedron (Fe 3+ O 3 (OH) (H 2 O) 2 [SO) and 4 ] - tetrahedra . The chains are held together by hydrogen bonds .

properties

The mineral is soluble in water and should therefore be stored away from moisture.

Education and Locations

Scaly aggregate with shiny, mica-like copiapite crystals from the Alcaparrosa mine, Cerritos Bayos, Calama , Antofagasta, Chile ( total size of the sample : 11.9 cm × 7.4 cm × 4.0 cm)

As a secondary mineral, copiapit is typically formed under the influence of acid mine water through weathering and oxidation of pyrite and other iron-containing sulfides or with the help of bacteria , e.g. B. Acidithiobacillus ferrooxidans (see also Acidithiobacillus ) in a wide range of rock types. However, due to its water solubility, the mineral is only stable in arid climates . In rare cases, copiapit can also arise from fumarole processes. Depending on the location, alunogen , amarantite , botryogen , butlerite , fibroferrite , halotrichite and melanterite can occur as accompanying minerals .

As a rather rare mineral formation, copiapite can sometimes be abundant at various sites, but overall it is not very common. So far, around 370 locations are known for Copiapit (as of 2016). In addition to its type locality Copiapó and the nearby Tierra Amarilla in the Atacama region, the mineral occurred in Chile on the peninsula near Mejillones and in the copper open-cast mine Chuquicamata in the Región de Antofagasta and at Cuya in the Región de Arica y Parinacota .

In Germany, Copiapit has been found in the Clara mine near Oberwolfach and the Wildsbach mine in Untermünstertal in Baden-Württemberg, a clay mine near Bad Freienwalde in Brandenburg, in Rammelsberg in Lower Saxony, in the Anna mine and the Julia , Christian Levin and collieries Auguste Victoria in North Rhine-Westphalia, the Friedrichssegen mine in Rhineland-Palatinate, in the quarries of the municipality of Nonnweiler in Saarland, the "Willi Agatz" mine near Dresden in Saxony and in the slate quarries near Lehesten in Thuringia.

In Austria, the mineral was found on the Hüttenberger Erzberg in Carinthia, near Amstall in Lower Austria, in the Hüttwinkltal / Raurisertal and near Mitterberg (municipality of Mühlbach am Hochkönig ) in Salzburg, in the Schlarbaum quarry near Klausen ( Bad Gleichenberg ) and on the zinc wall ( Schladminger) Tauern ) in Styria and in a gneiss quarry near Rufling in Upper Austria.

In Switzerland, Copiapit is so far only known from the Valle del Trodo near Magadino in the canton of Ticino and Saint-Luc and Granges (municipality of Sion ) in the canton of Valais.

Other locations include the Antarctic, Argentina, Australia, Belgium, Bolivia, Bulgaria, China, France, Greece, Iran, Ireland, Italy, Japan, Canada, Macedonia, Morocco, Mexico, New Zealand, Norway, Peru, Poland, Portugal, Romania, Russia, Slovakia, Sweden, Spain, South Africa, the Czech Republic, Ukraine, Hungary, the United Kingdom (England, Wales) and the United States of America.


See also

literature

Monographs
  • Heinrich Rose : About some iron oxide salts found in South America. In: Annals of Physics and Chemistry Volume 27 (1833), pp. 309–319 ( PDF 522.2 kB )
  • Copiapit. In: Wilhelm Haidinger: Handbook of determining mineralogy: containing the terminology, systematics, nomenclature and characteristics of the natural history of the mineral kingdom 2nd edition, Braumüller & Seidel, Vienna 1845, p. 489. Restricted preview in the Google book search
  • Charles Palache , Martin A. Peacock , Leonard G. Berry : Crystallography of copiapite. In: University of Toronto Studies: VI. Geological Series Volume 50 (1946), pp. 9–26 ( 1.02 MB )
Compendia

Web links

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

Individual evidence

  1. ↑ 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.  397 .
  2. ↑ a b c d e Copiapite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF kB )
  3. ↑ a b c d e Mindat - Copiapite
  4. ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p.  677 .
  5. ↑ Webmineral - Copiapite
  6. ^ Leonard G. Berry : Composition and optics of copiapite. In: University of Toronto Studies: VI. Geological Series. Volume 51 (1947), pp. 21–34 ( PDF 467.2 kB )
  7. ↑ Beatrix Brömme, Herbert Pöllmann: Synthesis, crystal chemistry and application of compounds with copiapite and voltaite structure Martin Luther University Halle-Wittenberg, Institute for Geological Sciences, Mineralogy / Geochemistry Working Group ( PDF 414.8 kB )
  8. ↑ Entry on Copiapit. In: Römpp Online . Georg Thieme Verlag, accessed on January 23, 2016.
  9. ↑ Mindat - Number of locations for Copiapit
  10. ↑ Find location list for Copiapit in the Mineralienatlas and in Mindat