Gaotaiit

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Gaotaiit
General and classification
other names

IMA 1993-017

chemical formula
  • Ir 3 Te 8
  • Ir <1 Te 2
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		II / C.05
02.12.01.18
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  = 6.413 (4)  Å
Formula units Z  = 1
Physical Properties
Mohs hardness 3 ( VHN 20 = 94–177 kg / mm 2 , average 117 kg / mm 2 )
Density (g / cm 3 ) calculated: 10.00
Cleavage is missing
Break ; Tenacity brittle
colour steel black, shining white in incident light with a bluish tinge
Line color black
transparency opaque (opaque)
shine Metallic luster

Gaotaiite is an extremely rare mineral from the mineral class of " sulfides and sulfosalts " with the chemical composition Ir 3 Te 8 and thus, chemically speaking, an iridium telluride . As close relatives of the sulfides, the tellurides are placed in the same class.

Gaotaiite crystallizes in the cubic crystal system , but has so far only been found in the form of irregular grains and mineral aggregates from 0.05 to 0.2 mm in size or coarse in veins from 0.05 to 0.02 mm thick and 0.3 to 1, 0 mm length can be found. The ( opaque ) mineral, invisible in every form, shows a metallic sheen on the surfaces of the steel-black grains . In the reflected light microscope , however, Gaotaiit appears bright white with a bluish tinge. However, its line color is always black.

Etymology and history

Gaotaiit was first discovered in the Gaotai Cr-PGE deposit near the village of the same name, about 200 km north-northeast of Beijing (also Beijing ) in Chengde County in Hebei Province . The first description was in 1995 Zuxiang Yu, who named the mineral after its type locality .

The type material is kept in the collection of the Chinese Geological Museum in Beijing.

classification

Since the Gaotaiite was only recognized as an independent mineral in 1993 and this was only published in 1995, it is not yet listed in the 8th edition of the Strunz mineral classification, which has been outdated since 1977 . 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.29-40 . In the "Lapis system" this corresponds to the class of "sulfides and sulfosalts" and there the section "sulfides with [the molar ratio] metal: S, Se, Te <1: 1", where gaotaiite together with ferroscutterudite , iridisite (from currently not recognized by the IMA), Kieftit , Nickelskutterudit and Skutterudit form an independent but unnamed group (as of 2018).

The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, classifies the Gaotaiite 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 , Geversit , Hauerit , Insizwait , 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 the Gaotaiite to the class of "sulfides and sulfosalts" and there into 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 gaotaiite (Ir 3 Te 8 ), the mineral consists of iridium and tellurium in a molar ratio of 3: 8. This corresponds to a mass fraction (% by weight) of 36.10% iridium (Ir) and 63, 90% tellurium (Te).

However, the values ​​from nine microprobe analyzes of the type material showed an average composition of 35.6 Ir% and 62.8% Te as well as additional low contents of 0.2% copper (Cu), 0.2% sulfur (S) and 0.1 % Platinum , which represents part of the original elements ( substitution , diadochy).

Crystal structure

Gaotaiite crystallizes cubically in the space group Pa 3 (space group no. 205) with the lattice parameters a  = 6.413 (4)  Å and one formula unit per unit cell . Template: room group / 205

Education and Locations

Gaotaiit forms in ultramafic chromite - deposits and found himself in concentrates related soaps along the river Luan River near the village of Gaotai in the Chinese province of Hebei. As Begleitminerale yet dignified came here with chromite gold , iridium and osmium , the platinum variety Ferro platinum and minerals Erlichmanit, Iridisit , Laurit, magnetite and Shuangfengit on.

Apart from its type locality, no other sites for Gaotaiit are known (as of 2020).

See also

literature

  • 於 祖 相: 新 矿物 高 台 矿 - 银 的 暗 化 物 . In: Acta Mineralogica Sinica . tape 15 , no. 1 , 1995, p. 1–4 (Chinese, rruff.info [PDF; 206 kB ; accessed on April 24, 2020] English abstract: Yu Zuxiang: Gaotaiite - A new iridium telluride).
  • John Leslie Jambor , Nikolai N. Pertsev, Andrew C. Roberts: New mineral names . In: American Mineralogist . tape 81 , 1996, pp. 249–254 (English, rruff.info [PDF; 556 kB ; accessed on April 24, 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. 119 .

Web links

Individual evidence

  1. ↑ a b c d 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 24, 2020 .
  2. ^ A b c 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).
  3. ↑ a b c d e f g h i 於 祖 相: 新 矿物 高 台 矿 - 银 的 暗 化 物 . In: Acta Mineralogica Sinica . tape 15 , no. 1 , 1995, p. 1–4 (Chinese, rruff.info [PDF; 206 kB ; accessed on April 24, 2020] English abstract: Yu Zuxiang: Gaotaiite - A new iridium telluride).
  4. ↑ a b c Gaotaiite . 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; 63  kB ; accessed on April 24, 2020]).
  5. ↑ Catalog of Type Mineral Specimens - G. (PDF 77 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed April 24, 2020 .
  6. ↑ 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 .
  7. ↑ 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 24, 2020 .
  8. ↑ Gaotaiit. In: Mineralienatlas Lexikon. Stefan Schorn u. a., accessed on April 24, 2020 .
  9. ↑ David Barthelmy: Gaotaiite Mineral Data. In: webmineral.com. Retrieved April 24, 2020 (English).
  10. ↑ Find location list for Gaotaiite at the Mineralienatlas and at Mindat , accessed on April 24, 2020.