Aleksit

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Aleksit
Aleksite.jpg
Silvery-black aleksite crystal aggregate from Keystone Canyon , Nye County , Nevada, USA
General and classification
other names

IMA 1977-03

chemical formula PbBi 2 Te 2 S 2
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.GC.40a
06/02/03/02
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol ditrigonal-scalenohedral; 3  2 / m
Space group P 3 m 1 (No. 164)Template: room group / 164
Lattice parameters a  = 4.2423 (25)  Å ; c  = 79.73 (5) Å
Formula units Z  = 6
Physical Properties
Mohs hardness 2 ( VHN 20 = 40-65)
Density (g / cm 3 ) calculated: 7.80
Cleavage completely after {0001}
colour steel gray; on polished surfaces very light gray with a greenish tinge
Line color not defined
transparency opaque (opaque)
shine Metallic luster

Aleksite is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts " with the chemical composition PbBi 2 Te 2 S 2 and thus chemically a lead - bismuth - tellurium sulfide.

Aleksite crystallizes in the trigonal crystal system and is usually found in the form of platy grains up to about one millimeter in size. The mineral is in any form opaque ( opaque ) and points to the steel-gray surfaces a metallic luster . Under the reflected light microscope , polished surfaces appear very light gray with a greenish tinge. The line color of Aleksit has not yet been determined due to the small sample size.

With a Mohs hardness of 2, aleksite is one of the soft minerals that, if the size is appropriate, could be scratched with a fingernail, similar to the reference mineral gypsum (hardness 2).

Etymology and history

Aleksit was first discovered in the Gold -Mine Alekseevskoye in Stanovoy Range (Region Sutamsky) in the Russian Federation territory Far East belonging Republic of Sakha (Yakutia). It was first described in 1978 by AG Lipovetsky, Yu. S. Borodaev and EN Zav'yalov (Russian А. Г. Липовецкий, Ю. С. Бородаев, Е. Н. Завьялов ), who named the mineral after its type locality .

The type material of the mineral is kept at Gosudarst University , Moscow State University and in the Fersman Museum (Catalog No. 79060 ) of the Russian Academy of Sciences in Moscow (Russia).,

classification

Since the aleksite was only recognized as an independent mineral in 1977 and this was only published in 1978, 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.12-20 . In the "Lapis Classification", this corresponds to the class of "sulfides and sulfosalts" and then the department "sulfides with [ molar ratio ] Metal: S, Se, Te <1: 1" where Aleksit with Babkinit , Kochkarit , Poubait , Rucklidgeit , Saddlebackit an independent but unnamed group / the "group" forms (as of 2018).

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, classifies the aleksite in the division of "sulfarsenides, sulfantimonides, sulfbismutides". This is further subdivided according to the crystal structure and the possible presence of additional sulfur atoms, so that the mineral according to its composition can be found in the sub-section "Poly-Sulfarsenide", where it is the only member of the unnamed group with the system no. 2.GC.40a forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the aleksite to the class of "sulfides and sulfosalts" and there to the department of "sulfide minerals". Here he is together with Kochkarit and Hedleyit in the " Kochkarit group " with the system no. 02.06.03 within the subsection "Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 4: 3".

Chemism

The idealized chemical composition of aleksite (PbBi 2 Te 2 S 2 ) consists of one part lead (Pb) and two parts each of bismuth (Bi), tellurium (Te) and sulfur (S), which is a mass fraction (% by weight) of 21.94% Pb, 44.25% Bi, 27.02% Te and 6.79% S.

Microprobe analyzes on two samples of natural aleksite from the type locality Alekseevskoye (Sacha, Russian Federation) showed the slightly different chemical composition of 20.3 and 20.5% Pb, 46.0 and 45.5% Bi and both times 27.3 % Te and 6.3% S. Silver, antimony and / or selenium could not be detected. The results correspond to the empirical formulas Pb 0.94 Bi 2.11 Te 2.06 S 1.89 or Pb 0.95 Bi 2.10 Te 2.06 S 1.89 , which was idealized to the formula mentioned at the beginning.

Crystal structure

Aleksite crystallizes trigonal in the space group P 3 m 1 (space group  no.164 ) with the lattice parameters a = 4.2423 (25)  Å and c  = 79.73 (5) Å as well as six formula units per unit cell . Template: room group / 164

Education and Locations

Aleksit formed by hydrothermal processes in sulfide-bearing quartz - veins , where he in paragenesis with galena and gold as well as altaite , tetradymite , Rucklidgeit and other tellurides occur.

As a rare mineral formation, aleksite could only be detected in a few places, although almost 30 sites have been documented worldwide. In addition to its type locality, the Alekseevskoye gold mine in the Sakha Republic, the mineral was also found in the Russian Federation in the polymetallic gold deposit of the Berezitovy mine (also Berezitovoe ) in the Urusha-Oldoi ore, which is also located in the Far East. The area of the Amur Oblast , the Kochkar gold deposit near Plast in the Chelyabinsk Oblast (southern Urals), in the Hopunvaara area near Pitkjaranta (also Pitkäranta ) in the Republic of Karelia and at the Panarechka volcano in the Murmansk Oblast (north-western Russia).

The only known site in Austria so far is a former gold and silver mining area with abandoned tunnels and heaps near Langenleiten in the Fragant valley in Carinthia formed by the Goldberg Group .

Other previously known localities in Europe include a shed with a hydrothermally altered tonalite - Intrusion on "Duke Hill" ( Hertogenwald ) about 10 km southeast of Eupen in the Belgian province of Liege, the Trepča Stan Terg Mine in Trepča complex (District Mitrovica) in Kosovo, the mining districts Baita (Bihor) , Jolotca ( Harghita ) and Săcărâmb (also Sacarîmb , Sekeremb or Nagyag , Hunedoara county ) in Romania, Limarinho at Chaves in the district of Vila Real in Portugal, the polymetallic Skarnerzlagerstätte the Conchita mine in Estepona in the Spanish province of Málaga and the copper and gold ore mine Clogau St. Davids near Bontddu in Wales (see also gold mining in Wales ) in the United Kingdom.

Aleksit was also found in one or more places in Australia, Brazil, Bulgaria, China, Japan, Canada, Kazakhstan and in the US state of Nevada.

See also

literature

  • А. Г. Липовецкий, Ю. С. Бородаев, Е. Н. Завьялов: Алексит PbBi 2 Te 2 S 2 - Новый Минерал . In: Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva . tape 107 , no. 3 , 1978, p. 315–321 (Russian, rruff.info [PDF; 681 kB ; accessed on July 17, 2020] English translation: AG Lipovetsky, Yu. S. Borodaev, EN Zav'yalov: Aleksite, PbBi 2 Te 2 S 2 , a new mineral).
  • Michael Fleischer , Joseph Anthony Mandarino , GY Chao: New mineral names . In: American Mineralogist . tape 64 , 1979, pp. 652–659 (English, rruff.info [PDF; 755 kB ; accessed on July 17, 2020]).
  • Nigel J. Cook, Cristiana L. Ciobanu, Christopher J. Stanley, Werner H. Paar, Krister Sunblad: Compositional data for Bi-Pb tellurosulfides . In: The Canadian Mineralogist . tape 45 , no. 3 , 2007, p. 417–435 , doi : 10.2113 / gscanmin.45.3.417 (English, rruff.info [PDF; 2.5 MB ; accessed on July 17, 2020]).

Web links

Commons : Aleksite  - collection of images, videos and audio files
  • Aleksit. In: Mineralienatlas Lexikon. Stefan Schorn u. a., accessed on July 17, 2020 .
  • Aleksite. In: mindat.org. Hudson Institute of Mineralogy, accessed July 17, 2020 .
  • David Barthelmy: Aleksite Mineral Data. In: webmineral.com. Retrieved July 17, 2020 .
  • Aleksite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on July 17, 2020 .

Individual evidence

  1. ↑ a b c Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: July 2020. (PDF; 2.44 MB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, July 2020, accessed July 17, 2020 .
  2. ^ A b c Peter Bayliss: Crystal chemistry and crystallography of some minerals in the tetradymite group . In: American Mineralogist . tape 76 , 1991, pp. 257–265 ( minsocam.org [PDF; 1.1 MB ; accessed on July 17, 2020]).
  3. ↑ a b Michael Fleischer , Joseph Anthony Mandarino , GY Chao: New mineral names . In: American Mineralogist . tape  64 , 1979, pp. 652–659 (English, rruff.info [PDF; 755 kB ; accessed on July 17, 2020]).
  4. ↑ a b c d 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 .
  5. ↑ a b c d Aleksite . 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 July 17, 2020]).
  6. ↑ 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 July 17, 2020 .
  7. ↑ Aleksit. In: Mineralienatlas Lexikon. Stefan Schorn u. a., accessed on July 17, 2020 .
  8. ↑ Localities for Aleksite. In: mindat.org. Hudson Institute of Mineralogy, accessed July 17, 2020 .
  9. ↑ List of localities for aleksite in the Mineralienatlas and Mindat , accessed on July 17, 2020.