Pyrargyrite
| Pyrargyrite | |
|---|---|
 Overall size of the stage : 3.3 × 3 × 2.6 cm |
|
| General and classification | |
| other names |
|
| chemical formula | Ag 3 [SbS 3 ] |
|
Mineral class (and possibly department) |
Sulphides - island (Neso) sulpharsenides, etc., with no added sulfur |
|
System no. to Strunz and to Dana |
2.GA.05 ( 8th edition : II / E.07) 04/03/01/02 |
| Crystallographic Data | |
| Crystal system | trigonal |
| Crystal class ; symbol | ditrigonal-pyramidal; 3 m |
| Space group | R 3 c (No. 161) |
| Lattice parameters | a = 11.04 Å ; c = 8.72 Å |
| Formula units | Z = 6 |
| Frequent crystal faces | {10 1 0}, {11 2 0}, {10 1 1}, {10 1 2} |
| Twinning | according to (10 1 4) |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | 5.85 |
| Cleavage | clearly after {10 1 1}; very indistinct after {01 1 2} |
| Break ; Tenacity | shell-like, uneven |
| colour | dark red to gray black |
| Line color | cherry red |
| transparency | translucent to opaque |
| shine | Diamond luster |
| Crystal optics | |
| Refractive indices |
n ω = 3.084 n ε = 2.881 |
| Birefringence | δ = 0.203 |
| Optical character | uniaxial negative |
Pyrargyrite , also known as Dunkles Rotvalig (ore) , antimony silverblende , rubyblende or aerosite , is a common mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the trigonal crystal system with the chemical composition Ag 3 [SbS 3 ] and structurally belongs to the sulfosalts with silver and antimony .
Pyrargyrite usually develops prismatic or rhombohedral crystals , but is also found in the form of granular to massive aggregates from dark red to gray-black in color. The mostly only translucent or completely opaque pyrargyrite crystals show diamond luster on the crystal surfaces. The cleavage is significantly depending on the cleavage direction {10 1 1} to very indistinct after {01 1 2}.
Etymology and history
The well-known since the 16th century, albeit in different forms of writing traditional designation Rotgültig or Rotgültigerz (also ertz red gold , rod guilders ertz , red güldenes ore and similar) initially comprised two different, but similar looking minerals, namely Pyrargyrite and Proustit . The ore was named because of its striking red color, its dazzle- like sheen and its high silver content of almost 60%.
According to Abraham Gottlob Werner, a distinction has been made between dark and light red gold ore since 1789 , but it was not until 1804 that the chemist Joseph Louis Proust was able to clarify through his chemical analyzes that the red gold ores of antimony ( dark , Ag 3 SbS 3 ) and arsenic ( light , Ag 3 AsS 3 ) are two separate minerals.
In 1805, Selb gave the synonym Aerosit to a "dark red gold ore that occurs in the Kolywanian silver mine in Siberia".
The name rhombohedral ruby bezel was coined in 1824 by Friedrich Mohs .
The name pyrargyrite for dark red gold ore, which is still valid today, was coined by Ernst Friedrich Glocker in 1831 after the two ancient Greek words πῦρ pûr for “fire” and ἄργυρος argyros for “silver” due to its property of being able to easily melt a grain of silver in front of the soldering tube .
classification
Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the pyrargyrite belonged to the class of "sulfides and sulfosalts" and there to the general division of "sulfosalts (S: As, Sb, Bi = x)", where it together with Proustit , Pyrostilpnit , quadratit , samsonite and xanthocon formed the unnamed group II / E.07 .
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 pyrargyrite to the class of “sulfides and sulfosalts”, but in the newly defined section of “sulfoarsenides, sulfoantimonides and sulfobismuthides” " a. This is also further subdivided according to the crystal structure, so that the mineral, according to its structure, can be found in the subdivision of "island sulfarsenides (Neso-sulfarsenides) etc., without additional sulfur (S)", where it can only be found together with prostite forms the unnamed group 2.GA.05 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns pyrargyrite to the class of "sulfides and sulfosalts" and there in the department of "sulfosalts". Here it is together with Proustite in the "Proustite group" named after this mineral with the system number 03.04.01 within the subdivision of the " Sulphosalts with the ratio 3> z / y and the composition (A + ) i (A 2+ ) j [B y C z ], A = metals, B = semi-metals, C = non-metals ”.
Crystal structure
Pyrargyrite crystallizes trigonal in the space group R 3 c (space group no. 161) with the lattice parameters a = 11.04 Å and c = 8.72 Å as well as 6 formula units per unit cell .
properties
When exposed to light, the initially red to dark red colored pyrargyrite darkens over time until it appears almost black. The color of the streak remains cherry-red, however, which enables identification of the mineral in addition to its low Mohs hardness of 2.5 and a density of 5.85 g / cm³.
Pyrargyrite mainly contains silver (59.75%), antimony (22.48%) and sulfur (17.76%). Arsenic can also be contained in isolated cases .
Between pyrargyrite and the related prostite (Ag 3 [AsS 3 ]) there is a continuous mixed crystal row up to a minimum temperature of 360 ° C.
Education and Locations
Pyrargyrite often forms in hydrothermal veins . Magnificent crystals of pyrargyrite can be found in some German deposits, especially in Sankt Andreasberg as well as in Freiberg and other places in the Saxon Ore Mountains . Notable finds come from Slovakia , Bohemia , Romania , Spain , Sardinia and Chile . Today the most beautiful crystals of the mineral can be found in South and Central America .
In Mexico pseudomorphoses of silver (from Zacatecas ) or acanthite (from Guanajuato ) after pyrargyrite can also be found occasionally .
Other locations include various regions in Australia , China and Canada ; Hokkaidō , Honshū and Kyūshū in Japan ; Carinthia , Salzburg , Styria and Tyrol in Austria and various regions in the USA . A total of around 1300 sites are known to date (as of 2012).
See also
literature
- Ernst Friedrich Glocker (1831): Rothgülden or Pyrargyrit , in: Handbuch der Mineralogie , Verlag Ben Johann Leonhard Schrag, Nuremberg 1831, pp. 388–392 ( PDF 360.8 kB )
- Carl Hintze : Pyrargyrite. In: Handbook of Mineralogy. First volume. First division . 1st edition, Verlag Veit & Co., Leipzig 1904, pp. 1051-1069. ( available online at archive.org )
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 51 .
Web links
- Mineral Atlas: Pyrargyrite (Wiki)
- Pyrargyrite in the mineralogical collection of the Technical University of Berlin
Individual evidence
- ↑ a b c d e f 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. 119 .
- ^ A b c d Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 284-287 .
- ↑ a b c d Mindat - Pyrargyrite (English)
- ↑ Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 304 .
- ↑ a b GeoMuseum of the Clausthal University of Technology - Pyrargyrit
- ↑ Carl Cäsar von Leonhard, Karl Friedrich Merz, Johann Heinrich Kopp: Systematic-tabular overview and characteristics of the mineral bodies (see 103. Rothgueltigerz) in the Google book search
- ↑ Thomas Witzke : The discovery of Miargyrit
- ↑ Photo of an acanthite pseudomorphism based on pyrargyrite from Guanajuato, Mexico
- ↑ Mindat - localities for pyrargyrite