Versit

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Versit
General and classification
chemical formula PtSb 2
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.EB.05a ( 8th edition : II / C.05)
02.12.01.14
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic-disdodecahedral; 2 / m  3
Space group Pa 3 (No. 205)Template: room group / 205
Lattice parameters a  = 6.43  Å
Formula units Z  = 4
Physical Properties
Mohs hardness 4.5 to 5 ( VHN 50 = 726–766 kg / mm 2 )
Density (g / cm 3 ) calculated: 10.97
Cleavage not defined
colour steel gray; light gray on polished surfaces
Line color not defined
transparency opaque (opaque)
shine Metallic luster

Geversit is a seldom occurring mineral from the mineral class of "sulfides and sulfosalts" with the idealized chemical composition PtSb 2 and thus, chemically speaking, platinum antimonide . As close relatives of the sulfides, the antimonides are placed in the same class.

Geversit crystallizes in the cubic crystal system , but has so far only been discovered in the form of tiny grains and adhesions in platinum ores ranging in color from steel-gray to light-gray. The surfaces of the mineral, which is opaque in every form, have a metallic sheen .

Etymology and history

The mineral was first discovered in the Driekop platinum mine in the Sekhukhuneland district about 25 km northeast of Burgersfort in the Bushveld complex in South Africa . It was first described in 1961 by Eugen Friedrich Stumpfl (1931-2004), who had also discovered the mineral and named it after the South African geologist Traugott Wilhelm Gevers .

The type material of the mineral (Cotyp, CT) is kept in the Mines ParisTech (also École nationale supérieure des mines ; English: National School of Mines ) in Paris , France.

classification

Already in the outdated 8th edition of the mineral classification according to Strunz , the Geversit belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with M: S <1: 1", where together with aurostibite , cattierite , hauerite , laurite , Michenerite , penroseit , pyrite , sperrylite , trogtalite , vaesite and villamanínite the "pyrite series" with the system no. II / C.05 formed.

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , the mineral was given the system and mineral number. II / D.17-50 . In the "Lapis system" this also corresponds to the section "Sulphides with metal: S, Se, Te <1: 1", where Geversit together with Aurostibit, Cattierit, Changchengit , Dzharkenit , Erlichmanit , Fukuchilit , Hauerit, Insizwait , Kruťait , Laurit, Maslovit , Mayingit , Michenerit, Padmait , Penroseite, pyrite, Sperrylith, Trogtalit, Testibiopalladit , Vaesit and Villamanínit the "pyrite group" formed (as 2018).

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, classifies Geversit in the more general section of “Metal sulfides with M: S ≤ 1: 2”. However, 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 together with aurostibite, cattierite, dzharkenite, erlichmanite, fukuchilite, gaotaiite , hauerite, insizwaite, iridisite , kruťaite, laurite, penroseit, pyrite, sperrylite, trogtalite, vaesite and villamanínite the "pyrite group" with the system no. 2.EB.05a forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Geversit to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here it is also in the "pyrite group (isometric: Pa 3 )" with the system no. 02.12.01 to be found within the subsection “ Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 2 ”. Template: room group / 205

Chemism

According to the idealized (theoretical) composition of Geversit (PtSb 2 ), the mineral consists of 44.48% platinum and 55.52% antimony . The samples from the Driekop type locality in the Limpopo province with 45.0% platinum and 51.5% antimony came very close to this ideal composition .

In mineral samples from the Onverwacht platinum metal mine near Mashishing (formerly Lydenburg ) in the Mpumalanga province , however, a clear bismuth content of 12.8% was found, which replaces part of the antimony ( substitution , diadochia). In addition, a small amount of arsenic of 0.7% was found.

A mineral that as Bismutanalogon to Geversit having the ideal formula PTBI 2 can be considered, since 1972 under the name Insizwait known.

Crystal structure

Geversit crystallizes cubically in the pyrite structure in the space group Pa 3 (space group no. 205) with the lattice parameter a  = 6.43  Å ° and four formula units per unit cell . Template: room group / 205

properties

Physical Properties

Due to the small size of the previous Geversit finds in the microscopic range, neither the cleavage nor the fracture behavior of the mineral could be determined.

With a Mohs hardness of 4.5 to 5, which corresponds to a Vickers hardness (VH, English VHN) of 726 to 766 kg / mm 2 with a test force of 50 grams , Geversit is one of the medium-hard minerals and can, like the reference mineral apatite (hardness 5) can be scratched with a pocket knife .

The density calculated from the crystal data is 10.97 g / cm 3 .

Optical properties

The surface color of Geversit is usually steel gray. On polished surfaces, on the other hand, it appears more light gray or white with a strong metallic sheen.

Education and Locations

Geversit forms in platinum mineral concentrates that come from Pt-Fe-Ni-Cu deposits in ultramafic rocks . At its type locality , the platinum mining Driekop in South Africa, joined Geversit in paragenesis with native platinum and gold , copper and iron minerals chalcopyrite and pyrrhotite as well as other platinum metal -Mineralen Hollingworthit , Sperrylith and stibiopalladinite on.

In mineral samples from the Vozhmin massif (also Vozhma massif ; Russian: Вожминского массива ) with serpentinized wehrlite and Olivinit in to Finland corresponding landscape of North Karelia on the border with Russia came as a further assemblages still Heazlewoodite , dignified copper , magnetite , Tučekit and as a type mineral Vozhminit added.

As a rare mineral formation, Geversit could only be proven in a few places worldwide, whereby around 40 sites have been documented so far. In addition to those already mentioned, the mineral was also found in South Africa in the Sandsloot Mine and the Turfspruit Farm near Mokopane in Limpopo, near Mashishing (formerly Lydenburg ) and near Klerksdorp in the northwest province.

In Finland, Geversit was still able to work in some places in Lapland such as the Keivitsansarvi platinum metal deposit near Sodankylä and in Russia, among others, in the Burakovskii layer complex on Lake Onega in the Republic of Karelia , near Yekaterinburg (formerly Sverdlovsk ), in the regions belonging to Siberia Irkutsk and Krasnoyarsk , in the Sayan Mountains in southern Russia as well as in the republics of Buryatia and Sakha (also Yakutia ) in the Far East.

In Austria Geversit has so far only performed on Mitterberg near Sankt Stefan ob Leoben in Styria. Another possible location near Wolfsbach ( Drosendorf-Zissersdorf municipality ) in Lower Austria has not yet been confirmed.

Other locations include Egypt, Australia, Brazil, China, India, Canada, Myanmar, Norway, Poland, Tanzania, the United Kingdom (Scotland) and the United States of America (Alaska).

See also

literature

  • EF Stumpfl: Some new platinoid-rich minerals, identified with the electron microanalyser . In: Mineralogical Magazine . tape 32 , 1961, pp. 833–847 (English, rruff.info [PDF; 777 kB ; accessed on March 26, 2020]).
  • Michael Fleischer : New mineral names . In: American Mineralogist . tape 46 , 1961, pp. 1513–1520 (English, rruff.info [PDF; 587 kB ; accessed on March 26, 2020]).
  • 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. 322 .
  • Nathaniel E. Brese, Hans Georg von Schnering : Bonding trends in pyrites and a reinvestigation of the structures of PdAs 2 , PdSb 2 , PtSb 2 and PtBi 2 . In: Journal of Inorganic and General Chemistry . tape 620 , March 1994, p. 393-404 , doi : 10.1002 / zaac.19946200302 (English).

Web links

Individual evidence

  1. ↑ a b c d e 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.  104 (English).
  2. ↑ a b Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: March 2020. (PDF; 1729 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2020, accessed March 26, 2020 .
  3. ↑ a b c d e f g h i j k l Geversite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 62  kB ; accessed on March 26, 2020]).
  4. ↑ a b Geversite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 14, 2020 .
  5. ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  6. ^ John Bowles: Obituary Eugen Friedrich Stumpfl, 1931-2004. (PDF; 660 kB) In: cambridge.org. University of Cambridge , accessed March 26, 2020 .
  7. ^ EF Stumpfl: Some new platinoid-rich minerals, identified with the electron microanalyser . In: Mineralogical Magazine . tape 32 , 1961, pp. 833–847 (English, rruff.info [PDF; 777 kB ; accessed on March 26, 2020]).
  8. ↑ Catalog of Type Mineral Specimens - G. (PDF; 77 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed March 26, 2020 .
  9. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed March 26, 2020 .
  10. ↑ Louis J. Cabri, DC Harris: The new mineral insizwaite (PtBi 2 ) and new data on niggliite (PtSn) . In: Mineralogical Magazine . tape 38 , 1972, p. 794-800 (English, rruff.info [PDF; 370 kB ; accessed on March 26, 2020]).
  11. ^ Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  254 .
  12. ↑ Micrograph with Geversit (white), Sudburyit (cream white) and Paolovit (light pink) In: mindat.org. Hudson Institute of Mineralogy, accessed March 26, 2020 .
  13. ↑ NS Rudashevskii, YP Men'shikov, AA Lentsi, NI Shumskaya, AB Lobanova, GN Goncharov, AG Tutov: Вожминит - (Ni, Co) 4 (As, Sb) S 2 - Новый Минерал . In: Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva . tape 111 , no. 4 , 1982, pp. 480–485 (Russian, rruff.info [PDF; 505 kB ; accessed on March 26, 2020] English translation of the title: Vozhminite, (Ni, Co) 4 (As, Sb) S 2 , a new mineral).
  14. ↑ Localities for Geversite. In: mindat.org. Hudson Institute of Mineralogy, accessed March 26, 2020 .
  15. ↑ Find location list for Geversit in the Mineralienatlas and Mindat , accessed on March 26, 2020.