Achávalite

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Achávalite
Achavalite.jpg
Shiny metallic achávalite crystal from the Cacheuta mine, Mendoza, Argentina
General and classification
chemical formula FeSe
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.CC.05 ( 8th edition : II / B.09a)
08/02/11/11
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  = 3.64  Å ; c  = 5.95 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 2.5
Density (g / cm 3 ) calculated: 6.58
Cleavage not defined
colour gray to dark gray
Line color grey black
transparency opaque
shine Metallic luster

Achávalite is a very rarely occurring mineral from the mineral class of "sulfides and sulfosalts" with the chemical composition FeSe. Chemically speaking, achávalite is therefore an iron selenide , a compound from the selenide group of substances related to sulphides with a molar ratio of iron  :  selenium  = 1: 1.

Achávalite crystallizes in the crystal system , but has so far only been found in the form of granular to massive aggregates . The mineral is in any form opaque ( opaque ) and displays on the surfaces of gray to dark gray aggregates have a metallic luster .

Etymology and history

Achávalit was first discovered in the pit Cacheuta on the mountain Cerro de Cacheuta in the province of Mendoza belonging Sierra de Cacheuta Argentina. It was first described in 1939 by Juan Augusto Olsacher (1903-1964), who named it after Luis Achával (1870-1938). He was a professor at the Universidad Nacional de Córdoba and, together with Manuel Rio, author of the Geografia de Córdoba .

In Olsacher's first description and in many older publications, the mineral name can be found in the spelling achavalite (without acute above the a), which, however, does not correspond to the specifications for mineral naming of the International Mineralogical Association (IMA), founded in 1958 , after the, for example, minerals that have been named after a person, it must be ensured that the spelling of the name is used. The inconsistent spelling of their names in many minerals was corrected with the publication Tidying up Mineral Names: an IMA-CNMNC Scheme for Suffixes, Hyphens and Diacritical marks in 2008 and in Newsletter 28 of the IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) 2015 made up for some missing mineral names such as achávalite. Achávalit has been used internationally since then in the spelling with the associated acute.

classification

Already in the outdated 8th edition of the mineral classification by Strunz of Achávalit belonged to the mineral class of "sulfides and sulfosalts" and then to the Department of "sulfides with M: S = 1: 1", where he together with Breithauptit , Freboldit , Imgreit , Jaipurit , Kotulkit , Langisit , Nickelin , pyrrhotite , Sederholmit , Smythit and troilite the "NiAs-series" with the system number. II / B.09a .

In the last revised and updated Lapis mineral directory by Stefan Weiß in 2018 , which, out of consideration for private collectors and institutional collections, is still based on this classic system of Karl Hugo Strunz , the mineral was given the system and mineral number. II / C.19-60 . In the "Lapis system" this also corresponds to the class of "sulfides and sulfosalts" and there the section "Sulfides with metal: S, Se, Te ≈ 1: 1", where achávalite together with heathite , jaipurite, modderite , pyrrhotite, Smythit, Troilit and Westerveldit form an independent but unnamed group.

The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and was updated by the IMA until 2009, also classifies achávalite in the category of “metal sulfides, M: S = 1: 1 (and similar)”. However, this is further subdivided according to the predominant metals in the compound, so that the mineral can be found according to its composition in the sub-section "with nickel (Ni), iron (Fe), cobalt (Co) etc.", where it can be found together with Breithauptit , Freboldit , Hexatestibiopanickelit , Jaipurit, Kotulskit , Langisit , Nickelin , Sederholmit , Sobolevskit , Stumpflit , Sudburyit , Vavřínit and Zlatogorit the "nickel Ling Ruppe" with the system number. 2.CC.05 forms.

Likewise, the systematics of minerals used mainly in the English-speaking world, according to Dana, assigns achávalite to the class of "sulfides and sulfosalts" and there into the category of "sulfide minerals". Here, too, it is in the " nickelin group (hexagonal: P 6 3 / mmc ) " with system no. 08/02/11 within the subsection “Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 1”.

Crystal structure

Achávalite crystallizes hexagonally in the space group P 6 3 / mmc (space group no. 194) with the lattice parameters a  = 3.64  Å and c  = 5.95 Å as well as two formula units per unit cell . Template: room group / 194

Crystal structure of achávalite

  • looking parallel to the a-axis

  • looking parallel to the b-axis

  • looking parallel to the c-axis

  • in the standard crystallographic orientation

Color table: __ Fe     __ Se

Education and Locations

In its type locality Cacheuta Achávalit originated in the interspersed with selenium mineralization calcitic transitions of porphyry rock that a fine-grained mixture of Clausthalit , Naumannite , Klockmannit , Umangite , Berzelianit , Eukairit , Tyrrellit and Eskebonit form.

Apart from its type locality in Argentina, the mineral has so far (as of 2018) only been detected in the Yutangba selenium deposit in the Enshi autonomous district in the southwest of the Chinese province of Hubei . Another, unspecified location in the Sierra de Cacheuta in Argentina has not yet been confirmed.

See also

literature

  • Juan Olsacher: Achavalita, seleniuro de hierro. Nueva especie mineral . In: Boletin de la Facultad de Ciencias Exactas, Fisicas y Naturales . tape 2 , 1939, pp. 73-78 ( rruff.info [PDF; 370 kB ; accessed on October 22, 2019]).
  • ED Franz: X-ray data of the mixed phases in the system pyrite (FeS 2 ) - ferroselite (FeSe 2 ) / pyrrhotite (Fe S ) - achavalite (FeSe) . In: New yearbook for mineralogy, monthly books . 1972, p. 276-280 .
  • Handong Qian, Zhenghua Zhao, Xiang Zheng, Chengyi Lin, Jiahu Zeng, Xuemei Wu, and Wu Chen: Chalcomenite and its geological significance . In: Acta Geologica Sinica . tape 80 , no. December 11 , 2006, pp. 1706–1710 , doi : 10.1111 / j.1755-6724.2006.tb00317.x .
  • Vladimir G. Krivovichev, Marina V. Charykova, Andrey V. Vishnevsky: The Thermodynamics of Selenium Minerals in Near-Surface Environments . In: Minerals . tape 7 , no. 10 , 2017, p. 188 , doi : 10.3390 / min7100188 .

Web links

Commons : Achávalite  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e f 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.  85 .
  2. ↑ David Barthelmy: Achavalite Mineral Data. In: webmineral.com. Accessed May 27, 2019 .
  3. ↑ a b Achávalite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 27, 2019 .
  4. ↑ Olsacherite . 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; 68  kB ; accessed on October 22, 2019]).
  5. ↑ Ernest H. Nickel , Joel D. Grice: The IMA Commission on New Minerals and Minerala Names: Procedures and Guidelines on Mineral Nomenclature . In: The Canadian Mineralogist . tape  36 , 1998, pp. 8–9 (English, cnmnc.main.jp [PDF; 336 kB ; accessed on May 27, 2019]).
  6. ^ Ernst AJ Burke: Tidying up Mineral Names: an IMA-CNMNC Scheme for Suffixes, Hyphens and Diacritical marks . In: Mineralogical Record . tape 39 , no. 2 , 2008, p. 131–135 (English, cnmnc.main.jp [PDF; 2.8 MB ; accessed on May 27, 2019]).
  7. ↑ Ulf Hålenius, Frédéric Hatert, Marco Pasero, Stuart J. Mills: IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) - Newsletter 28 . In: Mineralogical Magazine . tape 79 , no. 7 , December 2015, p. 1859–1864 (English, cnmnc.main.jp [PDF; 81 kB ; accessed on May 27, 2019] Achávalite, IMA 15-E, p. 1864).
  8. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: March 2019. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, September 2019, accessed October 22, 2019 .
  9. ↑ 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 .
  10. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed May 27, 2019 .
  11. ↑ List of localities for achávalite in the Mineralienatlas and Mindat , accessed on October 22, 2019.