Guérinit
| Guérinit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Ca 5 [(AsO 3 OH) 2 | (AsO 4 ) 2 ] • 9H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.CJ.75 ( 8th edition : VII / C.24) 02.39.02.02 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Room group (no.) | P 2 1 / n (No. 14) |
| Lattice parameters |
a = 17.63 Å ; b = 6.73 Å; c = 23.47 Å β = 90.6 ° |
| Formula units | Z = 5 |
| Physical Properties | |
| Mohs hardness | 1.5 |
| Density (g / cm 3 ) | measured: 2.68 to 2.76; calculated: 2.74 |
| Cleavage | well parallel to the longitudinal axis |
| Break ; Tenacity | brittle |
| colour | colorless, white |
| Line color | White |
| transparency | translucent to opaque |
| shine | Glass gloss, pearlescent |
| Crystal optics | |
| Refractive indices |
n α = 1.574 to 1.576 n β = 1.582 n γ = 1.582 to 1.584 |
| Birefringence | δ = 0.008 |
| Optical character | biaxial negative |
| Axis angle | 2V = 7 to 5 ° |
Guérinite is a rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical composition Ca 5 [(AsO 3 OH) 2 | (AsO 4 ) 2 ] · 9H 2 O, so it is a complex, water-containing calcium arsenate.
Guérinit develops wedge-shaped, prismatic crystals up to about three millimeters in length and a glass-like sheen , which are usually arranged in the form of tufted, spherulitic or rosette-shaped mineral aggregates . In its pure form, Guérinit is colorless and transparent. However, due to the multiple refraction of light due to the polycrystalline formation, it usually appears white and opaque.
Etymology and history
Guérinit was first described in 1961 by Evgeni I. Nefedov (1910–1976), who named the mineral after the French chemist Henri Guérin (* 1906). This was the first time that the chemical compound was synthetically produced.
The mineral was discovered at two museum levels , one of which was called wapplerite (actually Rösslerite ) and came from the “Daniel” pit near Neustädtel (Schneeberg) in the Saxon Ore Mountains and the other as a pharmacolite from the Richelsdorf mountains in the eastern Hessian district of Hersfeld-Rotenburg came from. Both of these sites are therefore considered to be the type locality for Guérinite.
classification
In the outdated, but partly still in use, 8th edition of the mineral classification according to Strunz , the Guérinite belonged to the department of "Hydrous phosphates without foreign anions ", where together with Ferrarisite , Haidingerite , Mcnearite , Irhtemite , Phaunouxite , Picropharmakolite , Rauenthalite and Vladimirite the " Haidingerit Group "with the system no. VII / C.24 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 Guérinite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the sub-section “Only with large cations”, where it is the only member of the unnamed group 8.CJ.75 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking area , also assigns Guérinite to the class of "phosphates, arsenates and vanadates", but there in the category of "hydrous acidic phosphates etc.". Here he can be found together with Vladimirit in the unnamed group 39.02.02 within the subdivision “ Hydrous acidic phosphates etc., H 2 (AB) 5 (XO 4 ) 4 × x (H 2 O)”.
Modifications and varieties
The compound Ca 5 [(AsO 3 OH) 2 | (AsO 4 ) 2 ] · 9H 2 O is dimorphic , so it also occurs as a triclinic crystallizing Ferrarisite in addition to the monoclinic Guérinite .
Education and Locations
Guérinite forms secondarily as a weathering product in arsenic-rich mineral deposits , where it occurs, among other things, in paragenesis with realgar , erythrin , quartz and calcite .
As a rare mineral formation, Guérinite could only be proven at a few sites, whereby so far (as of 2014) around 40 sites are known. In addition to its type locality Grube "Daniel" near Neustädtel (Schneeberg), the mineral was found in Germany, among other things, in the "Anton" mine and a smithy dump in Heubach Valley and the "Alt St. Joseph" mine near Wittichen , the Clara mine near Oberwolfach and in rock samples during tunnel construction for federal highway 33 near Hornberg in Baden-Württemberg; in an amphibolite quarry near Mackenheim (Abtsteinach) , the Kurfürsten tunnel in the Iba cobalt district as well as the exchange shaft and peace shaft near Suss (Nentershausen) in Hesse; the "Samson" mine near Sankt Andreasberg in Lower Saxony; the " Enlightened Luck " mine near Wernigerode in Saxony-Anhalt and in shaft 139 (Abrahamhalde) near Lauta (Marienberg) and near Schlema in the Erzgebirge district in Saxony.
The only known site in Switzerland so far is the “Grand-Praz” mine near Ayer (Val d'Anniviers) in the canton of Valais.
Other locations include France, Greece, Morocco, the Czech Republic and the United States of America (USA).
Crystal structure
Guérinite crystallizes monoclinically in the space group P 2 1 / n (space group no. 14) with the lattice parameters a = 17.63 Å ; b = 6.73 Å; c = 23.47 Å and β = 90.6 ° and 5 formula units per unit cell .
See also
literature
- EI Nefedov (1961): Guerinite - novyi mineral. In: Materialy Vsesoyuz. Nauchno-Issled. Geological Institute 45 (Mineralog. Sbornik No. 2), 113–115
- Brief description in: American Mineralogist. Volume 47 (1962), p. 416 ( PDF 501.7 kB )
Web links
- Mineral Atlas: Guérinite (Wiki)
- American-Mineralogist-Crystal-Structure-Database - Guérinite
- Thomas Witzke : The discovery of Guérinit. Retrieved January 15, 2014 .
Individual evidence
- ↑ a b c d e 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. 489 .
- ↑ Webmineral - Guérinite
- ↑ Guérinite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.7 kB )
- ↑ a b c Mindat - Guérinite
- ↑ 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 .
- ↑ Thomas Witzke : The discovery of Guérinit. Retrieved January 15, 2014 .
- ↑ a b Mineralienatlas: Guérinite (occurrence)
- ↑ Find location list for Guérinite in the Mineralienatlas and in [Mindat]