Anyuiit

from Wikipedia, the free encyclopedia
Anyuiit
General and classification
other names

IMA 1987-053

chemical formula AuPb 2
Mineral class
(and possibly department) 		Elements - metals and intermetallic alloys
System no. to Strunz
and to Dana 		1.AA.15 ( 8th edition : I / A.01)
01.01.04.01
Crystallographic Data
Crystal system tetragonal
Crystal class ; symbol ditetragonal-dipyramidal; 4 / m  2 / m  2 / m
Space group I 4 / mcm (No. 140)Template: room group / 140
Lattice parameters a  = 7.39 (2)  Å ; c  = 5.61 (3) Å
Formula units Z  = 4
Physical Properties
Mohs hardness 2.5 to 3 (VHN 20 = 142 to 152.8; average 146)
Density (g / cm 3 ) calculated: 13.49
Cleavage is missing
Break ; Tenacity plastically deformable
colour silver gray to lead gray
Line color lead gray
transparency opaque (opaque)
shine Metal gloss, matt

Anyuiit ( Russian Анюйит ) is a very rarely occurring minerals from the mineral class of "elements (including natural alloys, intermetallic compounds, carbides, nitrides, phosphides and silicides)" with the idealized chemical composition AuPb 2 and is thus chemically seen a natural alloy of Gold and lead in a molar ratio of 1: 2. Since in natural anyuiites the lead can be partially replaced ( substituted ) by antimony , the formula is also given in various sources as Au (Pb, Sb) 2 .

Anyuiit does not crystallize like the pure metals gold and lead in the cubic , but in the tetragonal crystal system in the tetragonal crystal system . This phenomenon is also known as the intermetallic compound . Anyuiit could only be found in nature in the form of rounded, elongated to flattened, polymetallic grains 1 to 4 mm in size, in which it occurs in complex adhesions with solid lead. Within these intergrowths, Anyuiit typically forms platelet-shaped aggregates in the range from 1 to 50 μm in diameter and 100 to 900 μm in length, as well as prismatic crystals from 50 × 100 μm to 0.9 mm in length and silver-gray in color.

Fresh samples of the mineral are silver-gray in color and show a distinct metallic luster . Within one to two days, however, it takes on a lead-gray color due to superficial oxidation and becomes matt.

Etymology and history

Was first discovered in a Anyuiit soaps - deposit at Great Anjui in northeastern Siberia in the Russian region of Far East . The mineral was analyzed and described by LV Razin and GA Sideorenko, who named it after its type locality . The mineral description and the chosen name were submitted to the International Mineralogical Association (IMA) for examination in 1987 (IMA registration number : 1987-053 ) and recognized that same year. The publication of the new discovery followed in 1989 in the Russian journal Mineralogicheskii Zhurnal and was at the announcement of 1,991 new mineral name by John Leslie Jambor and Edward S. Grew in American Mineralogist reconfirmed.

The type material of the mineral is kept in the Fersman Museum in Moscow .

classification

In the outdated, but still in use 8th edition of the mineral classification according to Strunz , the anyuiit belonged to the department of "Metals and intermetallic alloys (without semimetals)", where together with auricuprid , bogdanovite , gold , hunchunite , copper , novodneprite , silver , tetra -Auricuprid and Yuanjiangit 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 assigns the Anyuiit 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. Novodneprit can be found here according to its composition in the subdivision "Copper Cupalite Family", where it only forms the unnamed group 1.AA.15 together with Khatyrkit and Novodneprit .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Anyuiit to the class and there in the department of the same name of "elements". Here he is together with Hunchunit and Novodneprit as namesake in the group " Anyuiit and related alloys " with the system no. 01.01.04 within the sub-section "Elements: Metallic elements other than the platinum group".

Chemism

The chemical compositions of three grains were determined using electron beam microanalysis :

  • Gold (Au): 32.6 / 34.3 / 36.7 wt%
  • Lead (Pb): 64.8 / 59.0 / 52.9% by weight
  • Antimony (Sb): 0.3 / 5.8 / 10.2% by weight

Silver (Ag) could only be detected in one sample with a proportion of 0.35% by weight.

The values obtained correspond to the empirical compositions (Au 1.051 Ag 0.022 ) Σ1.073 (Pb 1.985 Sb 0.015 ) Σ2.000 or Au 1.049 (Pb 1.713 Sb 0.287 ) Σ2.000 or Au 1.101 (Pb 1.507 Sb 0.493 ) Z2.000 . The idealized formula was simplified accordingly to AuPb 2 .

Crystal structure

Anyuiit crystallizes tetragonally in the space group I 4 / mcm (space group no. 140) with the lattice parameters a  = 7.39  Å and c  = 5.61 Å, as well as four formula units per unit cell . Template: room group / 140

Education and Locations

Anyuiit forms in small, Hercynian , ultra- basic gabbroids . In addition to solid gold and lead, other element minerals such as platinum , osmium and its variety iridosmin , rutheniridosmin and hunchunit are found as accompanying minerals ; Sulphides such as pyrite , chalcopyrite and iridium or osmium-containing laurite , oxides such as chromite ( chromite spinel ), hematite , ilmenite , titanium-containing magnetite and pyrrhotite, and the phosphate mineral apatite .

Anyuiit is one of the very rare mineral formations that is only known in a few samples from fewer than 10 sites worldwide (as of 2018). In addition to its type locality on the Great Anjui in the Far East, the mineral occurred in Russia on a platinum-gold soap in the Inagli massif belonging to the Aldan highlands and in a diamond mine near Mirny in the Sakha Republic (Yakutia) in eastern Siberia and in the soap deposit Verkhneivinsk the river Neiva close sysert in the Ural belonging to Sverdlovsk Oblast to light.

Furthermore, we know Anyuiit even from the mines Sandaogou in Huadian and Jinjing in Hunchun in the Chinese province of Jilin , from a peridotite - outcrop at Etang de Lherz in the French department of Ariège , from a polymetallic gold-arsenic deposits in Novodneprovsk on the field Aqmola in Kazakhstan and from copper schists near Lubin in the Polish Lower Silesian Voivodeship.

See also

literature

  • LV Razin and GA Sideorenko: Anyuiite, AuPb 2 , a new gold and lead intermetallide . In: Mineralogicheskii Zhurnal . tape 11 , no. 4 , 1989, pp. 88-96 (Russian).
  • John L. Jambor, Edward S. Grew: New Mineral Names . In: American Mineralogist . tape 76 , no. 1-2 , 1991, pp. 299–305 ( minsocam.org [PDF; 917 kB ; accessed on February 25, 2018]).
  • Anyuiite . 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; 61 kB ; accessed on February 25, 2018]).

Web links

Individual evidence

  1. ↑ a b c d e f g h John L. Jambor, Edward S. Grew: New Mineral Names . In: American Mineralogist . tape 76 , no. 1-2 , 1991, pp. 299–305 ( minsocam.org [PDF; 917 kB ; accessed on February 25, 2018]).
  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. ↑ a b Stefan Weiß: Gold minerals and their varieties . In: gold. Mineral, power and illusion: 500 years of gold rush (= Christian Weise [Hrsg.]: ExtraLapis . Volume 2 ). Christian Weise Verlag, 1992, ISBN 3-921656-23-0 , ISSN  0945-8492 , p. 42 .
  4. ↑ a b Anyuiite . 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; 61  kB ; accessed on February 25, 2018]).
  5. ↑ Webmineral - Anyuiite (English)