Insizwait

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Insizwait
Sobolevskite & Insizwaite.jpg
Micro-inclusions of insizwait (tin white) and sobolevskite (gray) in a cubanite - pentlandite - chalcopyrite matrix (gold) from the Oktyabr'skoye deposit near Norilsk , Putorana Mountains , eastern Siberia
General and classification
other names

IMA 1971-031

chemical formula
  • PtBi 2
  • Pt (Bi, Sb) 2
  • PtBiSb
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.EB.05a
02.12.01.15
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  = 6.625 (natural); 6.7014 (8) (synthetic)  Å
Formula units Z  = 4
Physical Properties
Mohs hardness 5 to 5.5 ( VHN 25 = 488-540, average 519 kg / mm 2 )
Density (g / cm 3 ) calculated: 12.8
Cleavage not defined
colour tin white
Line color not defined
transparency opaque (opaque)
shine Metallic luster

Insizwait is a seldom occurring mineral from the mineral class of "sulfides and sulfosalts" with the idealized chemical composition PtBi 2 and thus, from a chemical point of view, platinum dismutide . As close relatives of the sulfides, the bismuthides are placed in the same class.

Insizwait crystallizes in the cubic crystal system , but has so far only been found in the form of tiny, rounded grains up to around 120  μm . The mineral, which is opaque in every form, is tin-white in color and has a metallic sheen on the surface .

Etymology and history

HJ Wallbaum succeeded in presenting the synthetic compound PtBi 2 and deciphering the crystal structure as early as 1943.

Natural mineral formation Insizwait was first in a sample of solid Pyrrhotinerz discovered consisting of copper - nickel - PGE - deposit Insizwa near the "Waterfall- Gorge " at the Eastern Cape of South Africa come from. The sample was made available by Professor DL ​​Scholtz, who in 1936 also described the geology and mineralogy of the deposit.

The first description of Insizwait was in 1972 by Louis J. Cabri and DC Harris, who named the mineral after its type locality .

The type material of the mineral is listed in the Geological Survey of Canada under catalog no. 10400 (CT) and in the Mineralogical Collection of the Canadian Museum of Nature in Ottawa (Canada).

classification

In the outdated 8th edition of the mineral classification according to Strunz , Insizwait is not yet listed. 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. II / D.17-150 . In the “Lapis system” this corresponds to the class of “sulfides and sulfosalts” and there the section “Sulfides with metal: S, Se, Te <1: 1”, where Insizwait together with Aurostibit , Cattierit , Changchengit , Dzharkenit , Erlichmanit , Fukuchilit , Geversit , Hauerit , Krutaite (here: Krutaite ) Laurit , Maslovit , Mayingit , Michenerit , Padmait , Penroseite , pyrite , Sperrylith , Testibiopalladit , Trogtalit , 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 the Insizwait 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 Aurostibit, Cattierit, Dzharkenit, Erlichmanit, Fukuchilit, Gaotaiit , Geversit, Hauerit, Iridisit , Kruťait, Laurit, Penroseit, Pyrite, Sperrylite, Trogtalit, Vaesit and Villamanínit 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 hauerite to the class of "sulphides and sulphosalts" and there in the category of "sulphide 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 Insizwait (PtBi 2 ), the compound consists of 31.82% by weight of platinum and 68.18% by weight of bismuth .

The results of the five microprobe analyzes on the type material from Insizwait from South Africa, however, showed an average composition of 36.06% by weight platinum (Pt) and 52.02% by weight bismuth and 12.88% by weight antimony , the one part of bismuth ( substitution , diadochie).

In the analysis of insizwait samples from the Sudbury District , Canada, foreign admixtures of 1.4% palladium (Pd), 0.17% nickel (Ni), 1.3% tin (Sn) and 7.7% tellurium (Te) . In contrast, the proportion of antimony was rather low at 2.4% (all data in% by weight).

Crystal structure

Insizwait crystallizes cubically in the pyrite structure in the space group Pa 3 (space group no. 205) with the lattice parameters a  = 6.625  Å (synthetic 6.7014 (8)) and four formula units per unit cell . Template: room group / 205

The crystal structure of Insizwarit corresponds to the pyrite structure , with platinum atoms instead of iron atoms occupying the lattice sites of a face-centered cubic unit cell and dumbbell-shaped Bi 2 groups occupying the interstitial sites . The dumbbell axes are each aligned in different orientations parallel to the 3-fold axes of rotation, which is the reason for the lower symmetry class within the cubic system.

Crystal structure of Insizwait

  • looking parallel to the a-axis

  • looking parallel to the b-axis

  • looking parallel to the c-axis

  • spatial representation centered on the three spatial diagonals

Color table: __ Pt     __ Bi

Education and Locations

Insizwait is formed by hydrothermal processes and is found in coarse pyrrhotite ores . In addition to pyrrhotite, other sulphides such as argentopentlandite , chalcopyrite , cubanite , galena , mackinawite , parkerite , pentlandite and sphalerite , tellurides such as altaite and hessite , bismuthides such as froodite as well as magnetite, which belongs to the oxides and which are a natural alloy to the element minerals , occur as accompanying minerals counting niggliit .

As a rare mineral formation, Insizwait could only be proven at a few sites, whereby around 20 sites have been documented worldwide. In addition to its type locality Insizwa near the "Waterfall Gorge" on the Eastern Cape, the mineral was also found in South Africa in the Driekop platinum mine in the Sekhukhuneland district near Burgersfort and in the Overysel deposit and in the Sandsloot opencast mine near Mokopane in the Limpopo province .

So far, no locations for Insizwait are known in Europe.

Other locations are in the Sudbury District and Thunder Bay District in the Canadian province of Ontario , the Russian regions of Krasnoyarsk (Siberia), Khabarovsk and Transbaikalia (Far East) and the Republic of Karelia (northwestern Russia) as well as the platinum soap Fox Gulch on the Salmon River ( Bethel Census Area ) in Alaska (USA).

See also

literature

  • Louis J. Cabri, DC Harris: The new mineral insizwaite (PtBi2) and new data on niggliite (PtSn) . In: Mineralogical Magazine . tape 38 , 1972, p. 794-800 (English, rruff.info [PDF; 370 kB ; accessed on March 31, 2020]).
  • Michael Fleischer : New mineral names . In: American Mineralogist . tape 58 , 1973, p. 805–807 (English, rruff.info [PDF; 288 kB ; accessed on April 1, 2020]).

Web links

Commons : Insizwaite  - 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; 2.44 MB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2020, accessed April 1, 2020 .
  2. ↑ a b c d Insizwaite . 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 31, 2020]).
  3. ↑ a b c d 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 .
  4. ^ 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 (English).
  5. ↑ a b c d e f g Louis J. Cabri, DC Harris: The new mineral insizwaite (PtBi2) and new data on niggliite (PtSn) . In: Mineralogical Magazine . tape 38 , 1972, p. 794-800 (English, rruff.info [PDF; 370 kB ; accessed on March 31, 2020]).
  6. ^ A b 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 , no. 3 , March 1994, p. 393-404 , doi : 10.1002 / zaac.19946200302 (English).
  7. ↑ HJ Wallbaum: The crystal structures of Bi 2 Pt and Sn 2 Pt . In: Zeitschrift für Metallkunde . tape 35 , 1943, pp. 200-201 .
  8. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1.82 MB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed April 1, 2020 .
  9. ↑ Find location list for Insizwait. In: Mineralienatlas Lexikon. Stefan Schorn u. a., accessed on April 1, 2020 .
  10. ↑ Find location list for Insizwait in the Mineralienatlas and Mindat , accessed on April 1, 2020.