Dyscrasite

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Dyscrasite
Dyscrasite-22000.jpg
Dyscrasite grade from the “Uranium Mine No. 21 ", Příbram , Bohemia, Czech Republic (size: 4.5 × 4.5 × 3.3 cm)
General and classification
other names
  • Antimony silver or silver antimony
  • Discrase
  • Discretion
  • Spit (s) shiny silver or spit shiny silver or silver spike gloss
chemical formula Ag 3 Sb
Mineral class
(and possibly department)
Sulfides and sulfosalts
System no. to Strunz
and to Dana
2.AA.35 ( 8th edition : II / A.02)
02.02.01.01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-pyramidal; mm 2
Room group (no.) Pm 2 m (No. 25)
Lattice parameters a  = 3.01  Å ; b  = 5.21 Å; c  = 4.83 Å
Formula units Z  = 1
Frequent crystal faces {111}, {110}, {010}, {021}, {001}
Twinning according to (110) pseudo-hexagonal twins
Physical Properties
Mohs hardness 3.5 to 4, can be cut with a knife
Density (g / cm 3 ) measured: 9.712; calculated: 9.720
Cleavage imperfect after {110}, clearly after {001} and {011}
Break ; Tenacity uneven, brittle
colour silver-white to light yellow, lead-gray to black
Line color silvery white
transparency opaque
shine Metallic luster

Dyscrasite , also out of date as antimony silver, is a rather rare mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the orthorhombic crystal system with the idealized chemical composition Ag 3 Sb, i.e. it consists of silver and antimony in a ratio of 3: 1.

Dyskrasit rarely develops well-formed crystals with tabular to prismatic, cylindrical or pyramidal habit and striped, metallic shiny surfaces. Pseudo-hexagonal twin formations are also known . Usually it is found in the form of leafy or granular to massive mineral aggregates . Fresh samples are silver-white to light yellow in color, which, however, turns lead-gray to black over time.

With a Mohs hardness of 3.5 to 4, dyscrasite is one of the medium-hard minerals and can therefore be cut with a knife despite its brittleness.

Etymology and history

The mineral was first mentioned in 1782 by Torbern Olof Bergman (1735–1784) under the name Argentum nativum antimonio adunatum

In older German-language literatures, dyscrasite can be found under various names, for example in 1786 by Bergrath Selb and in 1796 by Abraham Gottlob Werner as Spiesglanz-Silber and in 1813 by Friedrich Hausmann as Silberspiesglanz . The mineral was given a more precise designation in 1821 by Karl Cäsar von Leonhard and in 1823 by August Breithaupt , who named it antimony-silver or silver antimony according to its composition .

Be still valid name Dyskrasit derives from that of François Sulpice Beudant coined term in 1832 Discrase after the Greek word δνσκρᾶσις or better δνσκρασία from for "bad mixture", which refers to the changing silver content in the compound.

The type locality is the area around Wolfach based on the chemical analyzes by Martin Heinrich Klaproth and the Wenzel mine near Oberwolfach based on analyzes by G. Markl and J. Otto in 1992 on the material found there.

classification

In the now outdated, but still common 8th edition of the mineral classification according to Strunz , the dyscrasite belonged within the sulphides to the division of "alloys and alloy-like compounds", where together with Allargentum it formed the unnamed group II / A.02 .

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 classifies the dyscrasite in the category of "alloys and alloy-like compounds". However, this is further subdivided according to the predominant metals in the compound, so that the mineral can be found according to its composition in the sub-section "Compounds of semi-metals with copper (Cu), silver (Ag), gold (Au)", where it can be found as the only member is the unnamed group 2.AA.35 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the dyscrasite to the class of "sulphides and sulphosalts" and there in the category of "sulphide minerals". Here he is the namesake of the "Dyskrasitgruppe" with the system no. 02.02.01 within the subsection " Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 3: 1 ".

Education and Locations

Dyscrasite (antimony silver) in calcite from Sankt Andreasberg in the Harz Mountains (exhibited in the Mineralogical Museum of the University of Bonn )

Dyskrasit formed in hydrothermally in ore - programs usually associated with native silver and other silver minerals such as, among others Akanthit , Pyrargyrite and Stromeyerite and other ores such Allemontit (mixture of stibarsen and solid arsenic or antimony), barite , calcite , galena and tetrahedrite .

As a rather rare mineral formation, dyscrasite can sometimes be abundant at various sites, but overall it is not very common. So far (as of 2013) around 160 sites are known to be known. In addition to its type locality Grube Wenzel near Oberwolfach , the mineral was found in Germany in a few other places in the Black Forest (Baden-Württemberg) as well as in Sinatengrün and Lam in Bavaria, in several pits near Sankt Andreasberg in Lower Saxony and in some places in the Saxon Ore Mountains .

The only previously known site in Switzerland is near Böttstein , where the mineral was found in a drilling carried out by NAGRA .

The uranium deposit Háje u Příbramě in Okres Příbram , Czech Republic, is known for its extraordinary dyskrasite finds, where crystals and twins up to five centimeters in size were found.

Other locations are among others in Australia, Bolivia, Chile, China, Finland, France, Italy, Canada, Kazakhstan, Morocco, Norway, Russia, Sweden, Slovakia, Spain, South Africa, Tajikistan and in several states of the USA.

Crystal structure

Dyscrasite crystallizes orthorhombically in the space group Pm 2 m (space group no. 25) with the lattice parameters a  = 3.01  Å ; b  = 5.21 Å and c  = 4.83 Å and one formula unit per unit cell .

See also

literature

  • FS Beudant: Deuxième genre. Antimony. Espèce unique. Discrase , in: Traité Élémentaire de Minéralogie , 2nd edition, Paris 1832, pp. 613–614 ( PDF 111.8 kB )
  • Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 115-116 .

Web links

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

Individual evidence

  1. 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.  58 .
  2. Webmineral - Dyscrasite
  3. ^ A b Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 115-116 .
  4. a b Dyscrasite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 60.9 kB )
  5. 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. 370 .
  6. ^ Torberni Bergman: Sciagraphia regni mineralis: Secundum principia proxima digesti , London 1783 (Latin) in the Google book search
  7. ^ Geomuseum TU Clausthal - Dyskrasit
  8. a b 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. 370 .
  9. MH Klaproth: Investigation of the Spießglanzsilbers von Wolfach , in: Contributions to the chemical knowledge of the mineral bodies , second volume, Rottmann, Berlin 1797, pp. 298-301 (see Mindat - type locality Wenzel Mine, Frohnbach valley, Oberwolfach, Wolfach, Black Forest, Baden-Württemberg, Germany )
  10. Mindat - Number of localities for dyscrasite
  11. a b Mindat - Dyscrasite
  12. Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 20 ( Dörfler Natur ).