Chalcomenite

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Chalcomenite
Chalcomenite-107144.jpg
Needle-like chalcomenite from the "El Dragón Mine", Antonio Quijarro province , Potosí, Bolivia (image width 4 mm)
General and classification
other names

Copper selenite

chemical formula Cu [SeO 3 ] • 2H 2 O
Mineral class
(and possibly department) 		Oxides and hydroxides (including V [5,6] vanadates, arsenides, antimonides, bismuthides, sulfites, selenites, tellurites, iodates)
System no. to Strunz
and to Dana 		4.JH.05 ( 8th edition : IV / K.06)
02.34.02.01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-disphenoidic; 222
Space group P 2 1 2 1 2 1 (No. 19)Template: room group / 19
Lattice parameters a  = 6.67  Å ; b  = 9.16 Å; c  = 7.40 Å
Formula units Z  = 4
Frequent crystal faces {110}, {120}, {101}
Physical Properties
Mohs hardness 2 to 2.5
Density (g / cm 3 ) measured: 3.35; calculated: [3.35]
Cleavage no
Break ; Tenacity shell-like
colour light blue to dark blue
Line color pale blue
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.712
n β  = 1.732
n γ  = 1.732
Birefringence δ = 0.020
Optical character biaxial negative

Chalcomenite is a rarely occurring mineral from the mineral class of the " oxides and hydroxides " (including V [5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates). It crystallizes in the orthorhombic crystal system with the chemical composition CuSeO 3 · 2H 2 O, so it is a water-containing copper selenite from the selenite group of substances .

Chalcomenite is mostly found in the form of crusty coatings or powdery coatings, which consist of tiny, needle-like to prismatic or tabular to wedge-shaped crystals . The crystals are transparent, light blue to intense blue and have a glass-like sheen on the surface .

Etymology and history

Chalkomenite was named based on its composition after the ancient Greek words Χαλκός [chalkos] for "copper" and Μήνη [mene] for "moon" as a description for the contained element selenium , which is named after the Greek moon goddess Selene .

Chalkomenit was first on the mountain Cerro de Cacheuta in the province of Mendoza belonging Sierra de Cacheuta discovered in Argentina and in 1881 by Alfred Des Cloizeaux and Augustin Alexis Damour described.

The type material of the mineral is stored in the Muséum national d'histoire naturelle in Paris, France (register no. 81.14) and in Harvard University in Cambridge, Massachusetts, USA (register no. 101210).

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , chalcomenite belonged to the mineral class of "oxides and hydroxides" (including V [5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates) and there to the division of the "sulfites, Selenite, Tellurite" where he together with Balyakinit , Cesbornit , Graemit , Juabit and Teineit the unnamed group IV / K.06 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 chalcomenite to the class of "oxides and hydroxides", but in the category of "arsenites, antimonides, bismuthides, sulfites" , Selenite, Tellurite ”. This is further subdivided according to the exact substance group and the possible presence of additional anions and / or water of crystallization , so that the mineral is classified in the sub-section “Selenite without additional anions; with H 2 O “is to be found, where it is the only member of the unnamed group 4.JH.05 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns chalcomenite to the class of "sulfates, chromates and molybdates" and there to the category of "selenites, tellurites and sulphites". Here it can be found together with Teineit in the unnamed group 34.02.02 within the sub-section “Selenite - Tellurite - Sulphites with A 2+ XO 3  × x (H 2 O)”.

Crystal structure

Chalcomenite crystallizes orthorhombically in the space group P 2 1 2 1 2 1 (space group no. 19) with the lattice parameters a  = 6.67  Å ; b  = 9.16 Å and c  = 7.40 Å as well as four formula units per unit cell . Template: room group / 19

The crystal structure of chalcomenite consists of two assemblies - square pyramids forming Cu 2+ O 3 (H 2 O) 2 and trigonal pyramids forming Se 3+ O 3 - which are linked via the corners and chains parallel to the b-axis [010] form. The chains are linked by Cu [5] polyhedra and Se [3] pyramids.

Modifications and varieties

The compound CuSeO 3 · 2H 2 O is dimorphic and occurs naturally in addition to the orthorhombically crystallizing chalcomenite as monoclinic crystallizing clinochalkomenite .

Education and Locations

Deep blue, brilliant glass Chalkomenitkristalle as drusen filling from the Pakajake Canyon ( Pacajake Canyon ) Chayanta , Potosí, Bolivia ( total size : 4.3 cm × 3.1 cm × 2.4 cm)
Chalcomenite surrounded by klockmannite from the Sierra de Umango , La Rioja Province , Argentina (field of view: 5 mm)

Chalcomenite is a secondary mineral that is formed by weathering from umangite and klockmannite in the oxidation zone of copper- and selenium-containing deposits . As a rare mineral formation, the mineral could only be proven at a few sites, whereby so far (as of 2013) around 40 sites are known.

At its type locality Cerro de Cacheuta in the province of Mendoza, the mineral occurred in paragenesis Umangite, Clausthalite , Molybdomenite and Schmiederite . It was also found in Argentina in several places in the Vinchina department and in the Sierra de Cacho and Sierra de Famatina in the La Rioja province . In Bolivia, chalcomenite was found together with cobaltomenite , molybdomenite and penroseit in the "Hiaco Mine" in Pakajake Canyon ( province of Chayanta ) and together with allophane , basaluminite , clinochalkomenite and malachite in the "El Dragón Mine" ( province of Antonio Quijarro ) in the Potosí department become.

In Germany, the mineral is known so far only from the “Trogtal” quarry near Lautenthal in Lower Saxony, the copper chamber near Hettstedt in Saxony-Anhalt and the “Lichtenberg” open-cast mine near Ronneburg in Thuringia.

Other locations include Australia (Western Australia), China (Hubei), France (Auvergne), Ireland (County Kerry), Italy (Sardinia), Canada (Saskatchewan), the Democratic Republic of the Congo (Katanga), Mexico (Sonora) , Norway (Buskerud), Sweden (Östergötland), the United Kingdom (England) and the United States of America (Arizona, Colorado, Nevada, Utah).

See also

literature

Web links

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

Individual evidence

  1. ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
  2. ↑ Webmineral - Chalcomenite
  3. ^ A b c Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  273 .
  4. ↑ Chalcomenite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF kB )
  5. ↑ a b Mindat - Chalcomenite
  6. ↑ Mindat - Number of localities for Chalkomenite
  7. ↑ Find location list for chalcomenite at the Mineralienatlas and at Mindat