Köttigit
| Köttigit | |
|---|---|
 |
|
| General and classification | |
| other names |
Zinc arsenic |
| chemical formula | Zn 3 [AsO 4 ] 2 • 8H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.CE.40 ( 8th edition : VII / C.13) 03/40/06/05 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / m (No. 12) |
| Lattice parameters |
a = 10.24 Å ; b = 13.41 Å; c = 4.76 Å β = 105.2 ° |
| Formula units | Z = 2 |
| Frequent crystal faces | {010}, {201}, |
| Physical Properties | |
| Mohs hardness | 2 to 3 |
| Density (g / cm 3 ) | measured: 3.33; calculated: 3.24 |
| Cleavage | completely after {010} |
| Break ; Tenacity | fibrous |
| colour | colorless, white, light carmine red, greenish gray |
| Line color | white to reddish white |
| transparency | translucent |
| shine | Wax sheen to greasy sheen, silk sheen on split surfaces |
| Crystal optics | |
| Refractive indices |
n α = 1.622 n β = 1.638 n γ = 1.671 |
| Birefringence | δ = 0.049 |
| Optical character | biaxial positive |
| Axis angle | 2V = 74 ° (measured), 72 ° (calculated) |
| Pleochroism | Visible: X = Y = colorless; Z = light red |
Köttigit , outdated also known as zinc arsenate , is a rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates".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 of Zn 3 [AsO 4 ] 2 · 8H 2 O and is therefore chemically seen a hydrous zinc - arsenate .
Köttigit mostly develops needle-like to prismatic crystals up to 6 cm in length, but also occurs in the form of radial or tufted mineral aggregates , fibrous crusts and coarse masses. In its pure form, Köttigit is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it usually appears translucent white and due to foreign admixtures it can take on a light carmine-red and due to mixed crystal formation with parasymplesite (Fe +3 2 [AsO 4 ] 2 · 8H 2 O) a gray-blue to gray-green color. The crystal surfaces have a wax-like to grease-like sheen , whereas the cracked surfaces have a more silk-like shimmer .
Etymology and history
Köttigit was first discovered in the Daniel pit near Neustädtel (Schneeberg) in the Saxon Ore Mountains and described in 1850 by James Dwight Dana , who named the mineral after the German chemist Otto Friedrich Köttig (1824-1892). He had chemically analyzed the mineral for the first time.
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Köttigit belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates without foreign anions ", where together with Annabergit , Arupit , Barićit , Bobierrit , Cattiit , Erythrite , Hörnesit , Manganohörnesit , Pakhomovskyit , Parasymplesit and Vivianit the "Vivianitgruppe" with the system no. VII / C.13 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 Köttigit 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 and the molar ratio of the phosphate, arsenate or vanadate complex to the water of crystallization contained , so that the mineral is classified in the sub-section “With only medium-sized cations; RO 4 : H 2 O ≤ 1 "is found, where it together with Annabergit, Arupit, Barićit, Erythrin, 2.5 Ferrisymplesit , Hörnesit, Manganohörnesit, Pakhomovskyit, Parasymplesit and Vivianit in the" Vivianitgruppe "with the system number . 8.CE.40 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Köttigit to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates, etc.". Here he is also in the " Vivianite group " with the system no. 40.03.06 within the subsection "Water-containing phosphates etc., with (A 2+ ) 3 (XO 4 ) 2 × x (H 2 O)".
Crystal structure
Köttigit crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a = 10.24 Å ; b = 13.41 Å; c = 4.76 Å and β = 105.2 ° as well as two formula units per unit cell .
Education and Locations
Köttigit forms secondary from skutterudite and sphalerite in the oxidation zone of some zinc deposits . As accompanying minerals may include Adamin , gypsum , Legrandit , Metaköttigit , Symplesit and Parasymplesit , Pharmakosiderit and Skorodit occur.
As a rare mineral formation, Köttigit could only be detected at a few sites, whereby so far (as of 2015) slightly more than 60 sites are known. In addition to its type locality Grube Daniel near Neustädtel (Schneeberg), the mineral also appeared in Saxony near Bad Schlema and the “Sauberg” mines near Ehrenfriedersdorf , “Father Abraham” near Lauta (Marienberg) and “St. Johannes ”at Wolkenstein . Köttigit was also found in Germany in several places in the Black Forest in Baden-Württemberg, such as the Clara mine near Oberwolfach; in Hesse on the ore - halden of Richelsdorfer smelter; in some places in the Harz Mountains in Lower Saxony such as in the Glücksrad mine near Oberschulenberg and in the mining area of Sankt Andreasberg ; near Stolberg , Ramsbeck and the Brüderbund mine in North Rhine-Westphalia as well as near Bad Ems and the Friedrichssegen mine in the Rhineland-Palatinate Rhine-Lahn district.
In Austria, Köttigit has so far only been found in the Windbachgraben near the Habach Valley and on two slag heaps belonging to the Astenschmiede between Bucheben and Kolm-Saigurn in the Rauris Valley in the Salzburg High Tauern .
Other locations include Australia, Chile, Greece, Ireland, Italy, Japan, Mexico, Morocco, Namibia, Poland, Portugal, Russia, Slovakia, the Czech Republic, the United Kingdom (England) and the United States of America (Nevada , New Jersey, Utah, Utah).
See also
literature
- James Dwight Dana : Köttigite. In: A System of Mineralogy 3rd edition, George P Putnam, New York and London 1850, pp. 487–487 ( PDF 70.1 kB )
- BD Sturman: New data for köttigite and parasymplesite. In: The Canadian Mineralogist. Volume 14 (1976), pp. 437-441 ( PDF 348.6 kB )
- Roderick J. Hill: The crystal structure of köttigite. In: American Mineralogist. Volume 64 (1979), pp. 376-382 ( PDF 770.1 kB )
Web links
- Mineral Atlas: Köttigit (Wiki)
- Thomas Witzke : Discovery of Köttigit
- Webmineral - Köttigite
- Database-of-Raman-spectroscopy - Köttigite
- American-Mineralogist-Crystal-Structure-Database - Köttigite
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. 481 .
- ↑ a b c d Köttigite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 67.1 kB )
- ↑ a b c d e f g Mindat - Köttigite
- ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
- ↑ James Dwight Dana : Köttigite. in: A System of Mineralogy 3rd edition, George P Putnam, New York and London 1850, pp. 487–487 ( PDF 70.1 kB )
- ↑ 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. 646 .
- ↑ a b List of localities for Köttigit in the Mineralienatlas and Mindat