Yuanjiangit

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Yuanjiangit
General and classification
other names

IMA 1993-028

chemical formula AuSn
Mineral class
(and possibly department) 		elements
System no. to Strunz
and to Dana 		1.AC.15 ( 8th edition : I / A.01)
01.01.02.03
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m
Space group P 6 3 / mmc (No. 194)Template: room group / 194
Lattice parameters a  = 4.32  Å ; c  = 5.51 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 3.5 to 4
Density (g / cm 3 ) measured: 11.7 to 11.9; calculated: 11.78
Cleavage is missing
colour silvery white
Line color black
transparency opaque (opaque)
shine Metallic luster
Other properties
Chemical behavior slightly soluble in aqua regia (aqua regia), slowly soluble in HCl or HNO 3

Yuanjiangite is a very rarely occurring mineral from the mineral class of the "elements (including natural alloys, intermetallic compounds, carbides, nitrides, phosphides and silicides)" with the chemical composition AuSn and is thus chemically a natural alloy of gold and tin in a molar ratio of 1 : 1.

Yuanjiangite crystallizes in the hexagonal crystal system , but so far could only be in the form of granular, spherical and pseudo-gritty mineral aggregates up to about 2 mm in size, with individual grains generally being less than 5  μm in size. It is very seldom found in Druze also in slightly larger, hexagonal prisms.

The mineral is opaque in every form. The surfaces of the silver-white grains show a clear metallic luster . Yuanjiangit leaves a black line on the whiteboard .

Etymology and history

Yuanjiangite was first discovered in the fluvio-glacial sediments of a gold- soap deposit on the Yuan Jiang River in Yuanling County (Hunan Province) in China. The mineral was scientifically described by Lichang Chen, Cuiqing Tang, Jianhong Zhang and Zhenyun Liu, who named it after its type locality .

Yuanjiangite was recognized as a separate mineral by the International Mineralogical Association (IMA) in August 1993 . The first description was published in 1994 in Acta Petrologica et Mineralogica in Chinese.

Type material of the mineral, that is, mineral specimens from the type locality, is stored in the Chinese Geological Museum and the Chinese Geosciences University in Beijing .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the yuanjiangite belonged to the mineral class of the "elements" and there to the department of "metals and intermetallic alloys (without semimetals)", where it together with Anyuiit , Auricuprid , Bogdanovit , Gold , hunchunit , copper , novodneprit , silver and tetra-auricuprid the "copper series" with the system no. I / A.01 formed.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also classifies the Yuanjiangite 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. Yuanjiangite is to be found here according to its composition in the subdivision "Indium-Tin-Family", where together with bronze and sorosite it forms the "bronze group" with the system no. 1.AC.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Yuanjiangit to the class and department of the same name of "elements". Here it is together with auricuprid and tetra-auricuprid in the " auricuprid group " with the system no. 01.01.02 to be found in the subsection "Elements: Metallic elements other than the platinum group".

Chemism

When analyzing a total of seven microsamples of the mineral from the type locality, a gold content of between 60.529 and 64.580% by weight and a tin content of 35.303 to 38.807% by weight as well as small additions of silver and lead were found. This results in the empirical composition Au 1.008 Sn 0.988 , Pb 0.001 Ag 0.003 , which ideally corresponds to the formula AuSn.

Crystal structure

Yuanjiangite crystallizes hexagonally in the space group P 6 3 / mmc (space group no. 194) with the lattice parameters a  = 4.32  Å and c  = 5.51 Å and two formula units per unit cell . Template: room group / 194

The crystal structure corresponds to that of Nickelin .

properties

Yuanjiangit is readily soluble in aqua regia (aqua regia), slowly soluble in HCl or HNO 3

Education and Locations

In its type locality, the soap deposit on the Yuan Jiang River in China, Yuanjiangite was found to be closely interwoven with solid gold. In the same deposit , solid osmium and platinum as well as the minerals cinnabarite , diamond , cassiterite , pyrite , realgar , rutile and zircon could be detected.

The only other location (as of 2017) for Yuanjiangit is the Kockbulak gold and silver mine near Viloyati Sogd (also Viloyati Sughd, Viloyati Khodzhent, Viloyati Leninabad) about 10 km east of Angren and 3.5 km southwest of Kairagach in Tajikistan .

See also

literature

  • Lichang Chen, Cuiqing Tang, Jianhong Zhang, Zhenyun Liu: Yuanjiangite: A new auriferous and stanniferous mineral . In: Acta Petrologica et Mineralogica . tape 13 , no. 3 , 1994, p. 232–238 ( Original description in Chinese with a brief description in English ).
  • John Leslie Jambor , Jacek Puziewicz, Andrew C. Roberts: New Mineral Names . In: American Mineralogist . tape 80 , 1995, pp. 1328-133 ( rruff.info [PDF; 686 kB ; accessed on January 2, 2018] Yuanjiangit p. 3).
  • Yuanjiangite . 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; 93 kB ; accessed on January 2, 2018]).

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.  38 .
  2. ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
  3. ↑ 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. 6 .
  4. ^ A b c John Leslie Jambor , Jacek Puziewicz, Andrew C. Roberts: New Mineral Names . In: American Mineralogist . tape  80 , 1995, pp. 1328-133 ( rruff.info [PDF; 686 kB ; accessed on January 2, 2018] Yuanjiangit p. 3).
  5. ↑ a b Lichang Chen, Cuiqing Tang, Jianhong Zhang, Zhenyun Liu: Yuanjiangite: A new auriferous and stanniferous mineral . In: Acta Petrologica et Mineralogica . tape 13 , no. 3 , 1994, p. 232–238 ( Original description in Chinese with a brief description in English ).
  6. ↑ Mindat - Yuanjiangite locality, Yuan river placers (Yuanjiang placers), Yuanling Co., Huaihua Prefecture, Hunan Province, China
  7. ↑ Find location list for Yuanjiangit at the Mineralienatlas and at Mindat