Posnyakit
| Posnyakit | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1967-001 |
| chemical formula | Cu 4 [(OH) 6 | SO 4 ] • H 2 O |
|
Mineral class (and possibly department) |
Sulfates (and relatives) |
|
System no. to Strunz and to Dana |
7.DD.10 ( 8th edition : VI / D.03) 04/31/01/01 |
| Similar minerals | Langit |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | Pa (No. 7, position 3) |
| Lattice parameters |
a = 10.58 Å ; b = 6.34 Å; c = 7.86 Å β = 118.0 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 2 to 3 |
| Density (g / cm 3 ) | measured: 3.32; calculated: 3.35 |
| Cleavage | perfectly |
| Break ; Tenacity | uneven, brittle |
| colour | light blue to dark blue |
| Line color | Light Blue |
| transparency | translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.625 n β = 1.680 n γ = 1.706 |
| Birefringence | δ = 0.081 |
| Optical character | biaxial negative |
| Axis angle | 2V = 57 ° |
| Pleochroism | X = light blue to colorless; Y = blue to dark blue; Z = greenish blue to blue |
| Other properties | |
| Chemical behavior | Easily soluble in acids and ammonia, not soluble in water |
Posnjakit is a mineral from the mineral class of the " sulfates ( and relatives )", which can be partly abundant in different locations, but is generally not very common. It crystallizes in the monoclinic crystal system with the chemical composition Cu 4 [(OH) 6 | SO 4 ] • H 2 O and develops mostly tabular, pseudo-hexagonal crystals up to about 3 mm in size, but also granular to massive mineral aggregates and crusty or platy coatings from light to dark blue color with light blue line color .
Posnyakite crystals are translucent, break brittle with uneven fracture surfaces and show a glass-like sheen on their surfaces . With a Mohs hardness of 2 to 3, posnjakite is one of the soft minerals that, like the reference minerals gypsum (2) and calcite (3), can be scratched either with a fingernail or with a copper coin.
Etymology and history
Posnjakit was first discovered in the Wolfram (W) deposit of Nura-Taldy in the Karagandy Oblysy in Kazakhstan and described in 1967 by Aleksandr Ivanovich Komkov (1926-1987) and Yevgenii Ivanovich Nefedov (1910-1976), who named the mineral after the geochemist Eugene Valdemar Posnjak (1888–1949).
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the Posnjakite belonged to the mineral class of "sulfates, selenates , tellurates , chromates , molybdates and tungstates " and there to the department of "water-containing sulfates with foreign anions ", where they belong together with Christelit , Guarinoit , Ktenasit , Langite , Nakauriit , Namuwit , Ramsbeckit , Redgillit , Schulenbergit , Thérèsemagnanit and Wroewolfeit formed a distinct group.
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 Posnjakite to the class of "sulfates (selenates, tellurates, chromates, molybdates and wolframates)" and there in the department of "Sulphates (selenates, etc.) with additional anions, with H 2 O". However, this section is further subdivided according to the size of the cations involved and the crystal structure, so that the mineral can be classified in the sub-section “With only medium-sized cations; Layers of edge-linked octahedra "can be found, where together with guarinoite, langite, schulenbergite, thérèsemagnanite and wroewolfeit the" langite group "with the system no. 7.DD.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns posnjakite to the class of "sulfates, chromates and molybdates" and there to the category of "water-containing sulfates with hydroxyl or halogen". Here he is to be found as the only member of the unnamed group 04/31/01 within the subdivision of " Water-containing sulfates with hydroxyl or halogen with (A + B 2+ ) 4 (XO 4 ) Z q × x (H 2 O) ".
Crystal structure
Posnjakite crystallizes monoclinically in space group Pa (space group no. 7, position 3) with the lattice parameters a = 10.58 Å ; b = 6.34 Å; c = 7.86 Å and β = 118.0 ° and 2 formula units per unit cell .
Education and Locations
(size: 9.1 × 6.6 × 5.0 cm)
Posnjakite is usually formed by weathering in the oxidation zone of copper veins in paragenesis with other copper minerals such as azurite , brochantite , chalcopyrite , langite and malachite .
So far (as of 2015) around 300 sites are known worldwide, with the mineral in Kazakhstan only appearing at its Nura-Taldy type locality .
In Germany, Posnjakit was found in many places in the Black Forest in Baden-Württemberg such as B. in several pits near Wittichen and in the well-known pit Clara near Oberwolfach. Furthermore, the mineral was also used by Sommerkahl and Hagendorf ( Waidhaus ) in Bavaria; near Frankfurt am Main , Iba (Bebra) and Suss (Nentershausen) in Hesse; in several places in the Lower Saxony Harz such. B. Goslar and Sankt Andreasberg ; in several places in Niederbergisches Land and Sauerland as well as in Siegerland and in the Eifel from North Rhine-Westphalia to Rhineland-Palatinate; near Nothweiler , Werlau , Imsbach , Frücht , Wellmich and Rheinbreitbach in Rhineland-Palatinate; near Hasserode in Saxony-Anhalt; in many places in the Ore Mountains such as Schneeberg and Schmiedeberg and Horscha in Upper Lusatia in Saxony as well as Neumühle / Elster , Kamsdorf , Ullersreuth and the former dump near Ronneburg in Thuringia.
In Austria posnjakite has so far been found mainly in the regions of Carinthia , Salzburg , Styria , Tyrol and Vorarlberg .
In Switzerland, the mineral has so far been found in Mürtschenalp in the canton of Glarus , at Affeier in the canton of Graubünden , at Bex in the canton of Vaud and on Mont Chemin near Martigny and in several places in the municipality of Anniviers in the canton of Valais.
Other sites are among others in Australia, Azerbaijan, Belgium, France, Greece, Ireland, Italy, Japan, Canada, Morocco, Namibia, New Zealand, Norway, Poland, Portugal, Sweden, Slovakia, Slovenia, Spain, South Africa, the Czech Republic, the Ukraine , Hungary, the United Kingdom (Great Britain) and the United States of America (USA).
use
Posnyakite was known as a rare pigment in painting in the 15th and 16th centuries , but has been produced synthetically since the 19th century.
See also
literature
- M. Mellini, S. Merlino: Posnjakite: 2 ∞ [Cu 4 (OH) 6 (H 2 O) O] octahedral sheets in its structure. In: Journal of Crystallography. 149, Akademische Verlagsgesellschaft 1979, pp. 249-257.
Web links
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. 401 .
- ↑ Webmineral - Posnjakite
- ↑ a b Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 978-3-921656-70-9 , p. 210 .
- ↑ a b c Posnjakite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 68 kB )
- ↑ a b c d Posnjakite at mindat.org
- ↑ MINER Database, (c) Jacques Lapaire - Minéraux et étymologie ( Memento of the original of July 30, 2012 in the web archive archive.today ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (For full names and biographies of the first descriptors, see mineral names of Komkovite and Nefedovite)
- ↑ Mindat - Number of localities for Posnjakit
- ↑ Find location list for Posnjakit at the Mineralienatlas and at Mindat
- ↑ Cologne University of Applied Sciences - pigments containing copper ( Memento from October 26, 2014 in the Internet Archive )
