Enargit

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Enargit
Enargite-quartz-173234.jpg
Enargite on quartz from Silver Bow County , Montana, USA (size: 8.4 × 6.3 × 5.7 cm)
General and classification
chemical formula Cu 2 CuAsS 4
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.KA.05 ( 8th edition : II / B.07)
02/03/01/01
Similar minerals Manganite , stibnite , zinkenite
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-pyramidal; mm 2
Space group Pnm 2 1 (No. 31, position 2)Template: room group / 31.2
Lattice parameters a  = 6.44  Å ; b  = 7.41 Å; c  = 6.15 Å
Formula units Z  = 2
Frequent crystal faces tabular after {001}
Twinning occasionally crossing twins or star-shaped triplets along {320}
Physical Properties
Mohs hardness 3
Density (g / cm 3 ) measured: 4.45; calculated: 4.40
Cleavage completely according to {110}, clearly according to {100} and {010}
Break ; Tenacity uneven; brittle
colour steel gray to black, with a slight tinge of purple
Line color black
transparency opaque
shine glare-like metallic sheen

Enargite (also clarite , garbyite or guayacanite ) is a frequently occurring mineral from the mineral class of " sulfides and sulfosalts " with the chemical composition Cu 3 AsS 4 . Chemically, enargite consists of copper , arsenic and sulfur in a ratio of 3: 1: 4, but structurally it is one of the sulfarsenates related to sulfosalts.

Enargite crystallizes in the orthorhombic crystal system and develops mostly tabular to prismatic crystals up to 15 cm in size, striped along the c-axis , but can also be found in the form of coarse mineral aggregates from steel gray to black in color with black streak color . Occasionally, twins also form , with either interpenetrating twins or star-shaped triplets.

With a Mohs hardness of 3, enargite is still one of the medium-hard minerals that, like the reference mineral calcite, can be scratched with a copper coin. When crystalline, radiating form, enargite can look similar to manganite , and in later aggregates also to sphalerite .

Etymology and history

The mineral was found for the first time in the "San Francisco ore vein" near Morococha in the Peruvian province of Yauli and was described in 1850 by August Breithaupt , who used the Greek word έναργής for "visible" or " due to its clear to complete fissibility in all three spatial directions " recognizable "named.

classification

Already in the outdated 8th edition of the mineral classification according to Strunz , the enargite belonged to the department of "Sulphides with M: S = 1: 1", where together with stibioenargite, which was previously not recognized as an independent mineral species, it included the "enargite series" with the No. II / B.07 .

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this form of Karl Hugo Strunz's system , the mineral received the system and mineral number. II / C.14-10 . In the "Lapis system" this corresponds to the section "Sulphides with metal: S, Se, Te ≈ 1: 1", where enargite, together with agmantinite , argentopyrite , cubanite , sternbergite and stibioenargite, forms 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, assigns the enargite to the new section of “Sulfarsenates” and there in the subdivision “Sulfarsenates with (As, Sb) S 4 -Tetrahedra ", where he only works with Petrukit to create the" Enargite group "named after him with the system no. 2.KA.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the enargite to the section of "sulfosalts", where it is the only member of the unnamed group 03.02.01 within the sub-section " sulfosalts with the ratio z / y = 4 and the composition (A +) i (A2 +) j [ByCz], A = metals, B = semimetals, C = non-metals ”.

Crystal structure

Enargite crystallizes in the orthorhombic crystal system in the space group Pnm 2 1 (space group no. 31, position 2) with the lattice parameters a = 6.44  Å , b = 7.41 Å and c = 6.15 Å as well as 2 formula units per unit cell . Template: room group / 31.2

Modifications and varieties

Enargite is closely related to the minerals luzonite and famatinite . All three minerals have the chemical composition Cu 3 (As, Sb) S 4 . In contrast to enargite, however, luzonite and famatinite crystallize in the tetragonal crystal system . Enargite can contain a maximum of around 20% antimony , with larger contents always famatinite is formed.

Two varieties of enargite are known. One of these contains silver and the other tin .

A mineral described by Strunz in 1957 and designated as stibioenargite was not recognized by the IMA (founded in 1959), but classified as a possible antimony-containing variety of enargite or a hypothetical orthorhombic polymorph of famatinite.

Education and Locations

Prismatic, radially arranged enargite crystals from Pasto Bueno, Pallasca Province , Ancash , Peru

Enargite forms under hydrothermal conditions at temperatures of 280 to 600 ° C. It is often associated with pyrite , sphalerite , galena , bornite , tetrahedrite , tennantite , chalcosine , covelline , barite and quartz .

So far (as of 2011), Enargit has been found at around 740 sites worldwide. In addition to its type locality Morococha in the Junín region , where the largest enargite crystals with a length of up to 15 cm were also found, the mineral was found in many other regions of Peru . The "Luz Angelica Mine" near Quiruvilca (Santiago de Chuco) in the La Libertad region , which is also located in Peru, with crystal finds up to about 10 cm in size, is also worth mentioning because of its excellent enargite finds .

In Europe, the mineral can be found in Germany (Baden-Württemberg, Bavaria, Hesse, North Rhine-Westphalia, Rhineland-Palatinate, Saxony-Anhalt, Saxony), Austria (Carinthia, Salzburg, Styria, Tyrol), France , Serbia and Italy . Important deposits are in the Andes of South America, especially in Peru , Chile and Argentina . But also in the United States ( Montana , Utah , Arizona , Colorado ), Luzon ( Philippines ) and Japan are known.

use

Enargite is an important raw material for the extraction of copper .

literature

Web links

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

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.  82 (English).
  2. ↑ a b c d e f Enargite . 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 December 11, 2019]).
  3. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: November 2019. (PDF 1720 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, November 2019, accessed December 11, 2019 .
  4. ↑ 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. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed December 11, 2019 .
  6. ↑ a b Mihály Pósfay, Peter Buseck: Relationships between microstructure and composition in enargite and luzonite . In: American Mineralogist . tape 83 , 1998, pp. 373–382 ( minsocam.org [PDF; 939 kB ; accessed on December 11, 2019]).
  7. ↑ Argentian Enargite. In: mindat.org. Hudson Institute of Mineralogy, accessed December 11, 2019 .
  8. ↑ Stannoenargite. In: mindat.org. Hudson Institute of Mineralogy, accessed December 11, 2019 .
  9. ↑ Stibioenargite. In: mindat.org. Hudson Institute of Mineralogy, accessed December 11, 2019 .
  10. ^ 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.  850 (English).
  11. ↑ Find location list for enargite in the Mineralienatlas and Mindat , accessed on December 11, 2019.