Dufrenoysite

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Dufrenoysite
Dufrenoysite-291315.jpg
Dufrénoysite from the Binntal in the Swiss canton of Valais ( overall size: 7.3 × 5.7 × 3.2 cm)
General and classification
chemical formula
  • Pb 2 As 2 S 5
  • Oxide formula: 2 PbS · As 2 S 3
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.HC.05d ( 8th edition : II / E.18)
05/03/09/03
Similar minerals Baumhauerite , Rathite , Sartorite
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Room group (no.) P 2 1 (No. 4)
Lattice parameters a  = 7.90  Å ; b  = 25.7 Å; c  = 8.37 Å
β  = 90.3 °
Formula units Z  = 8
Physical Properties
Mohs hardness 3
Density (g / cm 3 ) measured: 5.50 to 5.57; calculated: 5.61
Cleavage completely after {010}
Break ; Tenacity clamshell; brittle
colour lead gray to steel gray
Line color reddish brown to chocolate brown
transparency slightly translucent to opaque
shine Metallic luster

Dufrénoysite is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the monoclinic crystal system with the composition PbAs 2 S 5 , so it is chemically a lead sulfarsenite .

Dufrénoysit develops extensive, longitudinally striped crystals with a tabular and rarely also needle-like habit of lead-gray to steel-gray color with reddish-brown to chocolate-brown streak color .

Etymology and history

Dufrénoysite was first discovered in the Lengenbach mine in the Binn valley in the Swiss canton of Valais . It was described in 1845 by Augustin Alexis Damour , who named the mineral after the French geologist and mineralogist Armand Dufrénoy . Julius Berendes treated the mineral in his dissertation in 1864.

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the Dufrénoysite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfosalts", where together with Veenit it formed the independent group II / E.18 .

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 Dufrénoysite to the class of "sulfides and sulfosalts", but there in the more finely divided section of "sulfosalts with SnS as a model" a. This department is further subdivided according to the predominant metals in the compound, so that the mineral, according to its composition, can be found in the subdivision “Only with lead (Pb)”, where it is named after the “Dufrénoysite group” with system no. 2.HC.05d and the other members Rathit , Rathit-IV and Veenit.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Dufrénoysite to the class of "sulfides and sulfosalts" and there in the department of "sulfosalts". Here he is together with Cosalit and Veenit in the "Cosalit group" with the system no. 03.05.09 within the subdivision of " sulfosalts with the ratio 2.5 <z / y <3 and the composition (A + ) i (A 2+ ) j [B y C z ], A = metals, B = semi-metals, C = non-metals ”.

Education and Locations

Needle-like dufrénoysite from Batopilas , Andres del Rio , Chihuahua , Mexico

Dufrénoysite forms hydrothermally at medium to low temperatures in dolomite . Accompanying minerals include chalcopyrite , sphalerite , realgar , auripigment and tetrahedrite .

As a rare mineral formation, Dufrénoysite has so far (as of 2012) only been proven at a few sites, around 30 sites are known to be known. In addition to its type locality Lengenbach, the mineral also appeared in Switzerland at the Messerbach, Turtschi and Reckibach in the Binntal .

Other locations include the “Beltana Mine” in South Australia , the Shuiquan gold deposits near Lianshan in China and Hemlo near Thunder Bay in Canada, the “Tynagh Mine” near Killimor in Ireland, Piano dei Camosci in the Italian municipality of Formazza , the “ Okoppe Mine ”in the Japanese district of Shimokita-gun on Honshū, Batopilas in the Mexican state of Chihuahua , Mine Bay on the Great Barrier Island of New Zealand, the“ Bleikvassli Mine ”in the Norwegian community of Hemnes , Wheal Boys (Trewetha Mine) near St. Endellion in England Cornwall as well as in various locations in several states of the USA.

Crystal structure

Dufrénoysite crystallizes monoclinically in the space group P 2 1 (space group no. 4) with the lattice parameters a  = 7.90  Å ; b  = 25.7 Å; c  = 8.37 Å and β = 90.3 ° and 8 formula units per unit cell .

See also

literature

Web links

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

Individual evidence

  1. ↑ IMA / CNMNC List of Mineral Names - Dufrénoysite (PDF 1.8 MB; p. 76)
  2. ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1979, ISBN 3-342-00288-3 , p.  352 .
  3. ↑ Webmineral - Dufrénoysite
  4. ↑ a b c d 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.  133 .
  5. ↑ a b John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Dufrénoysite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 62 kB )
  6. ↑ H. Baumhauer : The minerals of the Binnthal ( PDF 4.86 MB )
  7. ↑ Mindat - Number of localities for Dufrénoysite
  8. ^ Mindat - Dufrénoysite