Gersdorffit

from Wikipedia, the free encyclopedia
Gersdorffit
Gersdorffit - Lobenstein, Vogtland.jpg
General and classification
other names
  • Arsenic-nickel gloss or arsenic-nickel gravel
  • Nickel arsenic luster or nickel arsenic gravel
chemical formula NiAsS
Mineral class
(and possibly department)
Sulfides and sulfosalts
System no. to Strunz
and to Dana
2.EB.25 ( 8th edition : II / D.18)
02.12.03.02
Crystallographic Data
Crystal system cubic, orthorhombic
Crystal class ; symbol tetrahedral-pentagon-dodecahedral; 23 , cubic-disdodecahedral; 2 / m  3 , orthorhombic pyramidal; mm 2
Space group see section crystal structure
Physical Properties
Mohs hardness 5.5
Density (g / cm 3 ) 5.95 to 6.7
Cleavage good after {100}, {010} and {001}
Break ; Tenacity uneven
colour silver white to steel gray
Line color greyish black
transparency opaque
shine metallic luster

Gersdorffit also outdated as arsenic nickel gloss or arsenic nickel gravel or nickel arsenic gloss or nickel arsenopyrite known is a common mineral from the mineral class of "sulfides and sulfosalts" with the chemical composition NiAsS, that consists of equal parts of nickel , arsenic and sulfur .

Since 1986 the mineral has been divided into the three polytypes recognized by the International Mineralogical Association (IMA): Gersdorffit- P 2 1 3 , Gersdorffit- Pa 3 and Gersdorffit- Pca 2 1 , with Gersdorffit- P 2 1 3 and Gersdorffit- Pa 3 in cubic and Gersdorffit Pca 2 1 crystallize in orthorhombic symmetry . Template: room group / 198Template: room group / 205Template: room group / 29Template: room group / 198Template: room group / 205Template: room group / 29

Gersdorffit forms up to 4 cm large, octahedral or pyrite-like , typically striped crystals of silver-white to dark gray color.

Etymology and history

The mineral was found in 1845 by Löwe in its type locality Schladming in Austria . It is named after Johann von Gersdorff , the owner of the mine in which the mineral was found.

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the Gersdorffite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with the molar ratio of metal: sulfur, selenium, tellurium <1: 1", where he together with cobaltite , Hollingworthit , Irarsit , Jolliffeit , Kalungait , Milotait , Platarsit , Tolovkit , Ullmannit and Willyamit the "Cobaltit group" with the system number. II / D.18 .

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the IMA, also assigns the three polytypes Gersdorffit-P2 1 3, Gersdorffit-Pa3 and Gersdorffit-Pca2 1 , which are now independently recognized and newly defined , to the class of “sulfides and Sulphosalze ", but in the section on" Metal sulphides with M: S ≤ 1: 2 ". This is further subdivided according to the exact molar ratio and the predominant metals in the compound, so that the mineral can be found in the sub-section "M: S = 1: 2, with Fe, Co, Ni, PGE etc." according to its composition , where it is named after the "Gersdorffitgruppe" with the system no. 2.EB.25 and the other members Changchengit , Cobaltit, Hollingworthit, Irarsit, Jolliffeit, Kalungait, Krutovit , Maslovit , Mayingit , Michenerit , Milotait, Padmait , Platarsit, Testibiopalladit forms Tolovkit, Ullmannit and Willyamit.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Gersdorffit to the class of “sulfides and sulfosalts” and there to the “sulfide minerals” division. Here it is together with changchengite, cobaltite, hollingworthite, irarsite, jolliffeit, kalungaite, maslovite, michenerite, milotaite, padmaite, platarsite, testibiopalladite, tolovkite, ullmannite and willyamite in the " cobaltite group (cubic or pseudocubic system no.") . 02.12.03 within the subsection "Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 2".

Crystal structure

Gersdorffit crystallizes, depending on the polytype, either in the cubic or orthorhombic crystal system with the following lattice parameters . The respective room groups are part of the name:

  • Gersdorffit- P 2 1 3 (No. 198) crystallizes cubically with the lattice parameter a  = 5.6888  ÅTemplate: room group / 198
  • Gersdorffit- Pa 3 (no. 205) also crystallizes cubically with the lattice parameter a  = 5.7053 ÅTemplate: room group / 205
  • Gersdorffit- Pca 2 1 (No. 29) crystallizes orthorhombically (pseudocubic) with the lattice parameters a  = 5.622 Å; b  = 5.622 and c  = 5.622 ÅTemplate: room group / 29

The number of formula units per unit cell is four for all polytypes. It is likely that the individual phases can be converted into one another by changing the temperature.

properties

If you melt Gersdorffit in the blowtorch , is formed by the fuming of arsenic typical garlic smell and there remains a magnetic ball. In nitric acid , the mineral partially dissolves, the solution has a green color.

Modifications and varieties

corynite containing antimony

Gersdorffit is not a single mineral, but a group name for three polytypes, which have the same chemical composition but crystallize in different crystal systems.

Two varieties are known which contain antimony and cobalt, respectively. In the antimony-containing variety, which is also known under the names of antimony arsenic gloss or arsenic antimony nickel gloss , arsenic antimony nickel pebbles or corynite or korynite , the arsenic is partially replaced by antimony. It was found in Friesach (Austria), Bad Ems ( Germany ), as well as Bolivia , France , Russia and Slovakia . In the cobalt-containing variety, part of the nickel is replaced by cobalt. It also contains high levels of the platinum metals ruthenium , rhodium , iridium and osmium and has been found in China and Finland .

As arsenic antimony nickel gloss or Korynit but also iron and arsenic variety of Ullmannit is called.

Education and Locations

Gersdorffite forms in ore veins under hydrothermal conditions at medium temperatures. It is equipped with nickel, nickel Skutterudit , Cobaltit , Ullmannit , Maucherite , Löllingit , platinum metals, Millerit , pyrite , marcasite and chalcopyrite associated .

The mineral is widespread, but rich finds are rarely known. Gersdorffit can be found in Carinthia and Styria (Austria), Harz and Siegerland (Germany), Ontario ( Canada ), Tasmania ( Australia ) and Bolivia .

See also

literature

  • Peter Bayliss, NC Stephenson: The crystal structure of gersdorffite. In: Mineralogical Magazine. Volume 36 (1967), pp. 38–42 ( PDF 200.4 kB )
  • Gersdorffite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 59.7 kB )
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 461 (first edition: 1891).

Web links

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

Individual evidence

  1. Peter Bayliss: Subdivision of the pyrite group, and a chemical and X-ray diffraction investigation of ullmannite . In: The Canadian Mineralogist . tape 24 , 1986, pp. 27–33 ( rruff.info [PDF; 635 kB ; accessed on January 6, 2017]).
  2. Aloys J. Föcker, Wolfgang Jeitschko: The atomic order of the pnictogen and chalcogen atom in equiatomic ternary compounds TPnCh (T = Ni, Pd; Pn = P, As, Sb, Ch = S, Se, Te) . In: Journal of Solid State Chemistry . tape 162 , 2001, p. 69-78 , doi : 10.1006 / jssc.2001.9342 .
  3. a b Peter Bayliss: A further crystal structure refinement of gersdorffite . In: American Mineralogist . tape 67 , 1982, pp. 1058-1064 ( minsocam.org [PDF; 794 kB ; accessed on January 6, 2017]).
  4. a b Old mineral names and synonyms (PDF 2.65 MB)
  5. Antimonian Gersdorffite at mindat.org
  6. Cobaltoan Gersdorffite at mindat.org