Tetraferroplatinum

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Tetraferroplatinum
General and classification
other names

IMA 1974-012b

chemical formula PtFe
Mineral class
(and possibly department) 		elements
System no. to Strunz
and to Dana 		1.AG.40 ( 8th edition : I / A.15)
02/01/04/01
Crystallographic Data
Crystal system tetragonal
Crystal class ; symbol ditetragonal-dipyramidal; 4 / m  2 / m  2 / m
Space group P 4 / mmm (No. 123)Template: room group / 123
Lattice parameters a  = 2.73  Å ; c  = 3.64 Å
Formula units Z  = 1
Physical Properties
Mohs hardness not defined; VHN 100 = 384
Density (g / cm 3 ) measured: 14.3; calculated: 15.07
Cleavage is missing
colour steel gray, silver white
Line color not defined
transparency opaque (opaque)
shine Metallic luster
Other properties
Special features Ferromagnetic

Tetraferroplatinum is a rarely occurring mineral from the mineral class of the "elements (including natural alloys, intermetallic compounds, carbides, nitrides, phosphides and silicides)" with the chemical composition PtFe and is therefore chemically a natural alloy , more precisely an intermetallic compound of platinum and Iron in a ratio of ≈ 1: 1. Small foreign admixtures of copper (Cu), rhodium (Rh), iridium (Ir) and antimony (Sb) are also possible.

Tetraferroplatin crystallizes in the tetragonal crystal system , but has so far only been found in the form of tiny, rounded grains and flakes and as inclusions in other Pt-Fe alloys. The mineral is opaque in every form and shows a metallic sheen on the surfaces of the steel-gray to silver-white grains .

Etymology and history

Tetraferroplatinum, named after its tetragonal symmetry and composition, was recognized by the International Mineralogical Association (IMA) as an independent mineral in 1975 after the Pt-Fe alloys were redefined by Louis J. Cabri, Clive E. Feather . Accordingly, this designation applies to all platinum-iron alloys with an ordered structure and tetragonal symmetry close to the composition PtFe.

The nomenclature is based on the one hand on an investigation of the synthetic Pt-PtFe system and on the other hand on analyzes of natural mineral samples from the Tulameen and Similkameen rivers in the Canadian province of British Columbia , the gold mines on the Witwatersrand in the Transvaal and in the Orange Free State as well as the old ones Mooihoek platinum deposit ( Mooihoek Farm ) near Mashishing (formerly Lydenburg ) in South Africa and from the Stillwater complex in the US state of Montana. Accordingly, these sites are considered to be the type locality for tetraferroplatinum.

The terms ferroplatinum or tetragonal ferroplatinum , on the other hand, have been discredited and should no longer be used.

Type material , i.e. samples from the type localities required for a complete scientific description , is stored in the National Museum of Natural History in Washington, DC (USA) under catalog no. 136552 kept.

classification

Already in the outdated but still partially in use 8th edition of the mineral classification by Strunz of Tetra Ferro Platinum belonged to the mineral class of "elements" and then to the Department of "metals and intermetallic alloys (semimetals)" where he collaborated with Chengdeit , ferronickel platinum , Nielsenit , Isoferroplatinum and tulameenite formed the unnamed group I / A.15 .

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the IMA, also assigns tetraferroplatinum to the “Metals and intermetallic compounds” section. 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. According to its composition, tetraferroplatin can be found in the subdivision “ PGE metal alloys”, where the “tetraferroplatin group” named after him with the system number is only found together with ferronickel platinum and tulameenite. 1.AG.40 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns tetraferroplatin to the class and there in the department of the same name of "elements". Here he is also the namesake together with tulameenite, ferronickel platinum and potarit in the " tetraferroplatinum group (space group P 4 / mmm ) " with the system no. 02/01/04 within the sub-section "Elements: Platinum Group Metals and Alloys".

Chemism

The theoretical composition of PtFe consists of 77.74% platinum and 22.26% iron. Natural platinum alloys, however, always contain small amounts of foreign substances: In addition to the elements copper (Cu), rhodium (Rh), iridium (Ir) and antimony (Sb) already mentioned, proportions of nickel (Ni) and antimony (Sb) were also measured.

The empirical composition is therefore given as (Pt 1.03 Ir 0.01 ) Σ = 1.04 (Fe 0.69 Cu 0.24 Ni 0.02 Sb 0.01 ) Σ = 0.96 . The elements platinum and iridium or iron, copper, nickel and antimony indicated in the round brackets can represent each other in the formula ( substitution , diadochy), but are always in the same proportion to the other components of the mineral.

Crystal structure

Crystal structure of tetraferroplatinum

Tetraferroplatin crystallizes isostructural with tetra-auricupride (CuAu) in the tetragonal crystal system in the space group P 4 / mmm (space group no.123) with the lattice parameters a  = 2.72  Å and c  = 3.69 Å and one formula unit per unit cell . Template: room group / 123

The crystal structure of tetraferroplatin consists of alternating layers with platinum or iron atoms. It can also be described as consisting of two primitive, tetragonal unit cells ( square columns ), with either platinum (Pt) or iron (Fe) atoms at the 8 corner points. These two unit cells are pushed into one another by half a lattice parameter each, so that body-centered unit cells with Pt at the corners and Fe in the center or, conversely, Fe at the corners and Pt in the center. If Fe is assumed to be in the center, it is surrounded by 8 Pt and 4 Fe as the closest neighbors. One can also say that Fe is coordinated 8-fold to Pt and 4-fold to Fe .

Due to the slight differences in the atomic radii of platinum (135 pm) and iron (140 pm) and the regular arrangement of the two in the crystal lattice (superstructure), the structure as a whole is reduced to a tetragonal symmetry instead of forming a cubic substitution solid solution as in the cubic crystallizing starting metals platinum and iron would be expected.

Education and Locations

Tetraferroplatin formed in the South African Mooihoek in hortonolite-containing dunites , but can also arise in ultramafites and soap deposits derived from them, such as in the Urals (Russia). As Begleitminerale occur depending on the locality, among others, chalcopyrite , chromite , galena , Geversit , Irarsit , magnetite , Majakit , pentlandite , Plumbopalladinit , Sperrylith and Stannopalladinit on.

As a rare mineral formation, tetraferroplatin could only be detected at a few sites, with around 50 sites being documented so far.

In Canada, in addition to the Tulameen and Similkameen Rivers in British Columbia, the mineral was also found in alkali-rich rocks of the Coldwell Complex near Marathon and at the so-called Anaconda site in the Seeley Lake area near Thunder Bay in Ontario, in the Hall Chrome opencast mine in the municipality of Les Appalaches in Quebec and in the Cu-Ni-PGE deposit Wellgreen at Kluane found in Yukon.

In South Africa, in addition to the Mooihoek deposit ( Mooihoek Farm ) and the nearby Onverwacht mine near Lydenburg in the Mpumalanga province , tetraferroplatin also occurred in the Maandagshoek Farm deposit , the nearby Sandsloot and Zondereinde mines and the Booysendal Nord mine in the province's Bushveld complex Limpopo up.

Other well-known sites include Albania, Ethiopia, Australia, Brazil, China (Gansu, Xinjiang, Yunnan), the Dominican Republic, Indonesia, Japan, New Caledonia, Norway, Russia (Eastern Siberia, Far East), Tanzania and the United States ( Alaska, California, Montana, Oregon, Pennsylvania)

Tetraferroplatinum could also be detected in rock samples from the Mid-Atlantic Ridge , more precisely at the northeastern edge of the “Markov Depth” within the “Sierra Leone Fracture Zone” ( Sierra Leone Threshold ).

See also

literature

  • Louis J. Cabri, Clive E. Feather: Platinum-iron alloys; a nomenclature based on a study of natural and synthetic alloys . In: The Canadian Mineralogist . tape 13 , no. 2 , 1975, p. 117–126 , doi : 10.1007 / BF01164220 ( rruff.info [PDF; 1.1 MB ; accessed on January 15, 2018]).
  • Michael Fleischer , George Y. Chao and Joseph Anthony Mandarino : New Mineral Names . In: American Mineralogist . 6l, 197, p. 338-341 .
  • Peter Bayliss : Revised unit cell dimensions, space group, and chemical formula of some metallic minerals . In: The Canadian Mineralogist . tape 28 , 1990, pp. 751-755 ( rruff.info [PDF; 436 kB ; accessed on January 15, 2018]).
  • 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. 21-22 .

Web links

Individual evidence

  1. ↑ a b c d 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.  45 .
  2. ↑ Webmineral - Tetraferroplatinum (English)
  3. ↑ a b c d e 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. 21-22 .
  4. ↑ Mineral Atlas: Tetraferroplatinum
  5. ↑ a b c Louis J. Cabri, Clive E. Feather: Platinum-iron alloys; a nomenclature based on a study of natural and synthetic alloys . In: The Canadian Mineralogist . tape 13 , no. 2 , 1975, p. 117–126 , doi : 10.1007 / BF01164220 ( rruff.info [PDF; 1.1 MB ; accessed on January 15, 2018]).
  6. ↑ Type localities in the Mineralienatlas and Mindat
  7. ↑ a b Tetraferroplatinum . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF]).
  8. ↑ a b List of locations for tetraferroplatin in the Mineralienatlas and Mindat
  9. ↑ Mindat - Northeastern rim, Markov Deep, Sierra Leone fracture zone, Mid-Atlantic Ridge complex, Atlantic Ocean