Atokit

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Atokit
Atokite.jpg
Cubically distorted atokite crystal in paragenesis with isoferroplatinum from Komsomolski District , Khabarovsk Region , Far East Federal District , Russia
General and classification
other names

IMA 1974-041

chemical formula
  • Pd 3 Sn
  • (Pd, Pt) 3 Sn
Mineral class
(and possibly department) 		elements
System no. to Strunz
and to Dana 		1.AG.10
01.02.05.03
Crystallographic Data
Crystal system cubic
Crystal class ; symbol m-3mTemplate: crystal class / unknown crystal class
Space group Fm 3 m (No. 225)Template: room group / 225
Lattice parameters a  = 3.99  Å
Formula units Z  = 4
Frequent crystal faces {100}
Physical Properties
Mohs hardness 4.5 ( VHN 25  = 357)
Density (g / cm 3 ) calculated: 14.19
Cleavage not defined
colour white, light cream white on polished surfaces
Line color not defined
transparency opaque (opaque)
shine Metallic luster

Atokit is a very rarely occurring mineral from the mineral class of the "elements" with the idealized chemical composition Pd 3 Sn and thus a natural alloy of palladium and tin in a molar ratio of 3: 1. Atokit, however, forms a mixed crystal row with rustenburgite (Pt 3 Sn) , where palladium and platinum can represent one another. Correspondingly, in natural atokite mineral samples, part of the palladium is almost always replaced ( substituted ) by platinum . Therefore, the formula is generally also given as (Pd, Pt) 3 Sn.

Atokit crystallizes in the cubic crystal system and develops grains of up to 100 μm in size, tin-white in color with a metallic sheen on the surfaces.

Etymology and history

The mineral was first with Rustenburgit in Atok Mine in the Merensky Reef in the province of North West in South Africa found. The first description was made in 1975 by P. Mihálik, SA Hiemstra and JPR de Villiers, who named the mineral after its type locality .

classification

The atokit is not yet listed in the outdated 8th edition of the Strunz mineral classification . Only 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 , was the mineral given the system and mineral number. I / A.16-20 . In the "lapis system" this corresponds to the class of "elements" and there to the "metals and intermetallic compounds" department, where atokite forms an independent but unnamed group together with niggliite , palarstanide , plumbopalladinite , rustenburgite , stannopalladinite and zvyagintsevit (status no 2018).

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also classifies the atokit in the “Metals and Intermetallic Compounds” department. However, this is further subdivided according to the predominant metals in the compound, which have been divided into metal families according to their related properties. Atokit can be found here according to its composition in the sub-section “PGE metal alloys”, where together with Rustenburgit and Zvyagintsevit it forms the “Zvyagintsevit group” with system no. 1.AG.10 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the atokit to the class and division of the same name of "elements". Here he is together with Chengdeit , Isoferroplatin , Rustenburgit, Yixunit and Zvyagintsevit in the " Isoferroplatin group (room group Pm3m) " with the system no. 02/01/05 to be found in the subsection "Elements: Platinum Group Metals and Alloys".

Chemism

The microprobe analysis on the type material from the Merensky Reef showed an average composition of 43.74% platinum (Pt), 38.35% palladium and 18.65% tin (Sn). The empirical formula (Pd 1.94 Pt 1.21 ) Sn 0.85 was derived from the data and idealized to (Pd, Pt) 3 Sn.

Crystal structure

Atokit crystallizes in the cubic crystal system in the space group Fm 3 m (space group no. 225) with the lattice parameter a  = 3.99  Å and four formula units per unit cell . Template: room group / 225

Education and Locations

Atokit forms in platinum metal concentrates. Depending on the location, in addition to rustenburgite , various platinum tellurides or keithconnite and pallado arsenide can occur as accompanying minerals .

40 sites of the rarely occurring mineral are currently (as of 2020) documented. In addition to its type locality Atok mine and other finds in various pits in the Bushveld complex in the Limpopo province , the mineral also occurred in South Africa in the Impala platinum mine in the Rustenburg district in the northwest province . It was also found in the Hartley mine near Chiredzi (Masvingo province) in the state of Zimbabwe, north of South Africa.

So far, only one platinum metal soap is known within Europe on the Miessijoki River in the Finnish part of Lapland and several precious metal deposits in the European part of Russia, more precisely on the Kola Peninsula in Murmansk Oblast and in the Republic of Karelia in the federal district of northwestern Russia .

Other well-known sites are in the Canadian province of Ontario , in the Midu district in the Chinese province of Yunnan , in the republics of Buryatia and Sakha ( Yakutia ) in the Far East federation and in Irkutsk and Krasnoyarsk in the Siberia federation in Russia and in the Stillwater complex in US state of Montana .

See also

literature

  • P. Mihálik, SA Hiemstra, JPR de Villiers: Rustenburgite and atokite, two new platinum-group minerals from the Merensky Reef, Bushveld igneous complex . In: The Canadian Mineralogist . tape 13 , 1975, p. 146–150 (English, rruff.info [PDF; 403 kB ; accessed on March 18, 2020]).
  • Michael Fleischer , GY Chao, Joseph Anthony Mandarino : New mineral names . In: American Mineralogist . tape 61 , 1976, p. 338–341 (English, rruff.info [PDF; 543 kB ; accessed on March 18, 2020]).
  • Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York et al. 1997, ISBN 0-471-19310-0 , pp. 24 .

Web links

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

Individual evidence

  1. ↑ a b c 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 18, 2020 .
  2. ↑ 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.  43 (English).
  3. ↑ a b c d e f Atokite . 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; 61  kB ; accessed on March 18, 2020]).
  4. ↑ 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 .
  5. ↑ 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 18, 2020 .
  6. ↑ Michael Fleischer , GY Chao, Joseph Anthony Mandarino : New mineral names . In: American Mineralogist . tape  61 , 1976, p. 338–341 (English, rruff.info [PDF; 543 kB ; accessed on March 18, 2020]).
  7. ↑ Localities for Atokite. In: mindat.org. Hudson Institute of Mineralogy, accessed March 18, 2020 .
  8. ↑ Find location list for Atokit in the Mineralienatlas and Mindat , accessed on March 18, 2020.