Hongshiit

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Hongshiit
General and classification
chemical formula PtCu
Mineral class
(and possibly department)
elements
System no. to Strunz
and to Dana
1.AG.45 ( 8th edition : I / A.14)
02/01/03/01
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol ditrigonal-scalenohedral; 3  2 / m
Space group R 3 m (No. 166)Template: room group / 166
Lattice parameters a  = 10.71  Å ; c  = 13.19 Å
Formula units Z  = 48
Twinning after {11 2 1}
Physical Properties
Mohs hardness ≈ 4 ( VHN 50  = 204.3 ∥ a; VHN 50  = 276.8 ∥ c)
Density (g / cm 3 ) measured: 15.71; calculated: 15.63
Cleavage after {10 1 1}
Break ; Tenacity brittle, sometimes flexible and plastically deformable
colour lead gray to steel gray
Line color black
transparency opaque (opaque)
shine Metallic luster
Other properties
Chemical behavior insoluble in HCl and HNO 3

Hongshiit 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 PtCu and is therefore chemically a natural alloy , more precisely an intermetallic compound of platinum and Copper in a ratio of 1: 1.

Hongshiit crystallizes in the trigonal crystal system , but rarely develops microcrystalline, tabular crystals . It is usually found in the form of coarse, irregular grains up to about 1.5 mm in size or dendritic aggregates . The mineral is opaque in every form and shows a metallic sheen on the surfaces of the lead to steel-gray grains . His line color , on the other hand, is black.

Etymology and history

Hongshiit was first discovered in a platinum metal-containing ore deposit- close Hongshi , a village in the greater community Yangzi in the Chinese province of Hubei . The mineral was described in 1974 by Yu Zuxiang, Lin Shujen, Chao Pao, Fang Chingsung and Huang Chishun, who named it after its type locality .

The type material of the mineral is stored in the geological institute of the Chinese University of Geosciences in Beijing .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Hongshiite belonged to the mineral class of "elements" and there to the department of "metals and intermetallic alloys (without semimetals)", where it together with damiaoite , iridium , palladium , platinum , rhodium , Skaergaardit and Yixunit the "platinum series" with the system number. I / A.14 formed.

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies the Hongshiit in the department of "Metals and Intermetallic Compounds". 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. Hongshiit can be found here according to its composition in the subdivision "PGE metal alloys", where it only forms the unnamed group 1.AG.45 together with Skaergaardite .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Hongshiit to the class and there in the department of the same name of "elements". Here he is to be found as the only member of the unnamed group 01.02.03 within the subdivision "Elements: Platinum Group Metals and Alloys".

Chemism

In the initial description of the mineral, its composition, analyzed with the aid of the electron microprobe , is initially given as 61.0% by weight of platinum, 15.7% by weight of copper and 23.0% by weight of arsenic , which corresponds to the empirical formula Pt 1 , 02 Cu 0.81 As 1.00 or the idealized formula PtCuAs.

In a new analysis carried out eight years later on four grains with Pt-Cu alloys, an average composition of 74.93 wt.% Platinum and 24.52 wt.% Copper was determined. The high arsenic content found in the first analysis can be traced back to the inclusion of sperrylite . The formula has therefore been corrected accordingly and is now given as Pt 0.499 Cu 0.501 or idealized CuPt.

Crystal structure

Hongshiit crystallizes trigonally in the space group R 3 m (space group no. 166) with the lattice parameters a  = 10.71  Å and c  = 13.19 Å as well as 48 formula units per unit cell . Template: room group / 166

Education and Locations

At its type locality and so far the only place where it was found, Hongshi in China, Hongshiite formed in apatite- containing actinolithized diopside-platinum deposits where it replaced the previously formed cooperite (PtS). Hongshiite itself will in turn be replaced by isomerism over time . Further known Paragenesen from this place of discovery are Bornit , Diopsid , Epidot , Magnetit , Polydymit , Sperrylith and Vysotskit occurs.

Furthermore, Hongshiit found in highly haematitic courses in itabirites and typically surrounded by platinum was leached from the copper as including in the gold and iron mines Conceição and Cauê at Itabira , in the Brazilian state of Minas Gerais. Here the mineral addition to those already named Socialization occurred even with Atheneit , Sudovicovit , palladium-containing gold and tetra-auricupride than other accompanying minerals.

Hongshiit can also arise in alpine mafish - ultramafic intrusions and related soap deposits such as in the central mountain complex on the island of Rum in Scotland .

Other previously known sites (as of March 2018) include various soap deposits on the Kitagoha River in the North Kivu region in the Congo, on the Santiago River in the Ecuadorian province of Esmeraldas , on the Miessijoki and Sotajoki rivers in the Finnish region of Lapland and on the Oulankajoki in the neighboring Russian Republic of Karelia , on the Pustaya River on the Kamchatka Peninsula and on the Kondjor Massif in the Aldan Highlands in the Khabarovsk region on the Miass River near Chelyabinsk in the Urals in Russia, on the Salmon River in Goodnews Bay in the US state of Alaska and an alluvial Soap deposit near Vestřev in the Czech region of Bohemia.

See also

literature

  • Yu Zuxiang, Lin Shujen, Chao Pao, Fang Chingsung, Huang Chishun: A preliminary study of some new minerals of the platinum group and another associated new one in platinum-bearing intrusion in a region in China . In: Acta Geologica Sinica . tape 48 , no. 2 , 1974, p. 202-218 .
  • Michael Fleischer , Adolf Pabst , Joseph Anthony Mandarino , George Y. Chao, Louis J. Cabri: New Mineral Names . In: American Mineralogist . tape 61 , 1976, p. 174–186 ( minsocam.org [PDF; 1.6 MB ; accessed on February 12, 2018] Hongshiite from p. 12 with the formula PtCuAs).
  • Peng Zhizhong, Chang Chienhung, Ximen Lovlov: Discussion on published articles in the research of new minerals of the platinum group discovered in China in recent years . In: Acta Geologica Sinica . tape 4 , 1978, p. 326–336 (Chinese, rruff.info [PDF; 2.5 MB ; accessed on February 12, 2018] Hongshiite from p. 4 with the formula PtCuAs).
  • K. Ding: Further studies of the minerals “isoplatincopper” and “hongshiite” . In: Scientia Geologica Sinica . tape 2 , 1980, p. 168-171 .
  • Yu Zuxiang: New data on hongshiite . In: Bulletin of the Institute of Geology, Chinese Academy of Sciences . tape 4 , 1982, pp. 75–81 (Chinese with a brief description in English).
  • Pete J. Dunn, Louis J. Cabri, George Y. Chao, Michael Fleischer, Carl A. Francis, Joel D. Grice, John L Jambor, Adolf Pabst: New Mineral Names . In: American Mineralogist . tape 69 , 1984, pp. 406-412 ( minsocam.org [PDF; 835 kB ; accessed on February 12, 2018]).
  • Yu Zuxiang: New Data of Daomanite and Honghiite . In: Acta Geologica Sinica . tape 75 , no. 4 , December 2001, p. 458-466 .
  • Rogerio Kwitko, Alexandre R. Cabral, Bernd Lehmann, JH Gilles Laflamme, Louis J. Cabri, Alan J. Criddle, Henry F. Galbiatti: Hongshiite, PtCu, from itabirite-hosted Au-Pd-Pt mineralization (jacutinga), Itabira district , Minas Gerais, Brazil . In: Canadian Mineralogist . tape 40 , no. 2 , 2002, p. 711-723 , doi : 10.2113 / gscanmin.40.2.711 .

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. ^ A b c Yu Zuxiang: New Data of Daomanite and Honghiite . In: Acta Geologica Sinica . tape 75 , no. 4 , December 2001, p. 458-466 .
  3. a b c d e f g h Hongshiite . 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; 58  kB ; accessed on February 5, 2018]).
  4. Michael Fleischer , Adolf Pabst , Joseph Anthony Mandarino , George Y. Chao, Louis J. Cabri: New Mineral Names . In: American Mineralogist . tape  61 , 1976, p. 174–186 ( minsocam.org [PDF; 1.6 MB ; accessed on February 12, 2018] Hongshiite from p. 12 with the formula PtCuAs).
  5. Louis J. Cabri: Platinum group elements: mineralogy, geology, recovery . In: Canadian Institute of Mining, Metallurgy and Petroleum . tape 54 , 1981, pp. 109 .
  6. List of localities for Hongshiit in the Mineralienatlas and Mindat