Eukairite

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Eukairite
Eucairite-561857.jpg
Eukairite (creamy white) in matrix with greenish crust made of unknown material from the Cougar Mine, Slick Rock, San Miguel County (Colorado) , USA ( total size of the sample: 3.8 cm × 2 cm × 1.5 cm)
General and classification
other names

Selenium copper silver

chemical formula CuAgSe
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.BA.25d ( 8th edition : II / B.06)
04/02/06/02
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Pmmn (No. 59)Template: room group / 59
Lattice parameters a  = 4.10  Å ; b  = 20.35 Å; c  = 6.31 Å
Formula units Z  = 10
Physical Properties
Mohs hardness 2.5
Density (g / cm 3 ) measured: 7.6 to 7.8; calculated: 7.91
Cleavage is missing
Break ; Tenacity uneven to slightly scalloped; brittle, moderately cuttable
colour fresh pewter white to creamy white, tarnishing orange to brown
Line color gray-white metallic
transparency opaque
shine Metallic luster

Eukairit also outdated as selenium copper silver known is a rarely occurring mineral from the mineral class of "sulfides and sulfosalts" with the chemical composition CuAgSe, so there is an equal number of copper , silver and selenium . The mineral is one of the selenides related to sulphides .

Eukairit crystallizes in the orthorhombic crystal system , but developed no visible with the naked eye crystals . It is usually found in the form of granular masses or bubbles embedded in a matrix . The mineral is opaque in every form and, in fresh samples, has a tin-white to cream-white, metallic shine in color. After a while, eukairite samples turn orange to brown.

Etymology and history

Jöns Jakob Berzelius , the first to describe the eukairite

Eukairite was first discovered in the “Skrikerum” mine near Valdemarsvik in the Swedish province of Östergötland County (formerly Östergötland ). The mineral was first described in 1818 by Jöns Jakob Berzelius . He named it after the Greek word εὔκαιρος eukairos for "at the right time", as this mineral find was extremely cheap for his research into the discovery of the element selenium.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the eukairite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides, selenides and tellurides with a ratio of metal: S, Se, Te> 1: 1 ”, where together with Stromeyerite he created the“ Stromeyerite-Eukairit-Gruppe ”with the system no. II / B.06 and the other members Brodtkorbit , Henryit , Imiterit , Jalpait , Mckinstryit and Selenojalpait .

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 Eukairit in the category of "Metal sulfides, M: S> 1: 1 (mainly 2: 1)". This is, however, 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 "with copper (Cu), silver (Ag), gold (Au)", where it is the only member forms unnamed group 2.BA.25d .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns eukairite to the class of "sulfides and sulfosalts" and there into the category of "sulfide minerals". Here it is together with stromeyerite in the " stromeyerite group " with the system no. 04/02/06 within the subsection "Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 2: 1".

Crystal structure

Eukairite crystallizes orthorhombically in the space group Pmmn (space group no. 59) with the lattice parameters a  = 4.10  Å ; b  = 20.35 Å and c  = 6.31 Å and 10 formula units per unit cell . Template: room group / 59

properties

In front of the soldering tube , Eukairit melts with a strong smell of selenium (similar to garlic or rotting radish ) to a gray and soft, but not supple metal grain.

Education and Locations

Eukairite is mainly formed in hydrothermal selenium deposits . In addition to other selenium minerals such as berzelianite , chalcomenite , clausthalite , crookesite , klockmannite , tiemannite and umangite , calcite , malachite and weissite can be used as accompanying minerals .

As a rare mineral formation, Eukairite could only be detected at a few sites, although around 60 sites are known to date (as of 2016). Its type locality - Skrikerum mine in Östergötland is the only known site in Sweden so far .

In Germany, the mineral was found in the grape mine near Lerbach , the Trogtal quarries near Lautenthal and in the Roter Bär mine near Sankt Andreasberg in Lower Saxony; near Tilkerode ( Abberode ) in Lower Saxony and in shaft 371 in the Schlema - Hartenstein district in Saxony.

Other locations include Argentina, Australia, Bulgaria, Chile, China, France, Greenland, Canada, Norway, Poland, Romania, the Czech Republic, Uzbekistan, the United Kingdom (England) and the United States of America (Colorado, Nevada, Utah ).

See also

literature

  • Jöns Jakob Berzelius : III. Undersökning af några föreningar, som bero af svagare frändskaper 12. Undersökning om fórekommandet af selenium i mineralriket . In: Afhandlingar i Fysik, Kemi och Mineralogi . tape 6 , 1818, p. 134–144 ( rruff.info [PDF; 2.1 MB ; accessed on April 9, 2018]).
  • Friedrich Klockmann : Mineralogical communications from the collections of the Bergakademie zu Clausthal . In: Journal for Crystallography and Mineralogy . tape 19 , 1891, p. 265–275 ( rruff.info [PDF; 561 kB ; accessed on April 9, 2018]).
  • Lewis S. Ramsdell: The crystal structure of some metallic sulfides . In: American Mineralogist . tape 10 , 1925, pp. 281–304 ( rruff.info [PDF; 1.6 MB ; accessed on April 9, 2018]).
  • AJ Frueh (Jr.), GK Czamanske, C. Knight: The crystallography of eucairite, CuAgSe . In: Journal of Crystallography . tape 108 , 1957, pp. 389–396 ( rruff.info [PDF; 389 kB ; accessed on April 9, 2018]).

Web links

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

Individual evidence

  1. ↑ a b c Jöns Jakob Berzelius: The application of the soldering pipe in chemistry and mineralogy. Behavior of the minerals in front of the soldering pipe. Selenium and selenium metals. Selenium copper silver, Cu 2 Se + AgSe, eukairite . 4th, improved edition. Johann Leonhard Schrag, Nuremberg 1844, p. 124 ( limited preview in Google Book search).
  2. ↑ a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  65 .
  3. ↑ Dave Barthelmy: Eucairite Mineral Data. In: webmineral.com. Retrieved April 9, 2018 .
  4. ↑ a b c d Eucairite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 58  kB ; accessed on April 9, 2018]).
  5. ↑ 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 .
  6. ↑ 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.  302 .
  7. ^ Wilhelm Pape (edited by Max Sengebusch): Concise dictionary of the Greek language . 3. Edition. Vieweg & Sohn, Braunschweig 1914, p.  1073 ( zeno.org [accessed April 9, 2018]).
  8. ↑ 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. 317 (Selenium Minerals, No. 2) .
  9. ↑ Selenium: trace element with a radish scent protects the body from infections and chronic diseases. In: g-netz.de. Retrieved April 9, 2018 .
  10. ↑ Wolfgang Legrum: Fragrances, between stench and fragrance: Occurrence, properties and use of fragrances and their mixtures . Vieweg + Teubner, Wiesbaden 2011, p. 73 ( limited preview in Google Book search).
  11. ↑ Number of sites for Eukairit. In: mindat.org. Retrieved April 9, 2018 .
  12. ↑ Find location list for Eukairite in the Mineralienatlas. In: mineralienatlas.de. Retrieved February 21, 2016 . and at Mindat. In: mindat.org. Retrieved April 9, 2018 .