Enargite
Enargite (also Clarit, Garbyit or Guayacanit ) is a commonly occurring mineral from the mineral class of " sulfides and sulfosalts ," specifically the Sulfoarsenate. It crystallizes in the orthorhombic crystal system with the chemical composition Cu2CuAsS4 (Simplified Cu3AsS4 ) and developed mostly tabular to prismatic, along the c - axis striped crystals up to 15 cm in size, but also massive mineral aggregates of steel-gray to black in color with black stroke color. Occasionally, it also comes to twinning, either penetration twins or triplets stellate arise.
With a Mohs hardness of 3, which corresponds to that of the reference mineral calcite, heard Enargite to the soft minerals that can be scratched with a copper coin. With the formation of crystalline, strahliger form Enargite can see the manganite similar. In spätigen aggregates also the sphalerite.
Etymology and history
The mineral was first found in the " San Francisco lode " at Morococha in the Peruvian province Yauli and 1850 described by August Breithaupt, of the mineral due to its significant to perfect cleavage in all three spatial directions after the Greek word έναργής for visible or recognizable named.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the enargite belonged to the department of " sulfides with the molar ratio of metal: sulfur, selenium, tellurium = 1: 1 ," where he along with Argento pyrite, cubanite, Sternbergit and Stibioenargit the unnamed group II/C.14 formed.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the enargite other hand, in the new department of " Sulfoarsenate " and then in the sub-division " Sulfarsenate with (As, Sb) S4 tetrahedra ", where he sold with Petrukit named after him ". Enargitgruppe "with the system no 2.KA.05 forms.
The mostly commonly used in English-speaking classification of minerals according to Dana assigns the enargite in the department of " thio ", where he is the only member of the unnamed group 03:02:01 within the subdivision " sulfosalts with the ratio z / y = 4 and the composition (A ) i ( A2 ) j [ Bycz ], A = metals, semimetals B =, C = to find non-metals ".
Modifications and varieties
Enargite is closely related to the minerals and Luzonit Famatinit. All three minerals have the chemical composition Cu3 ( As, Sb ) S4. Unlike Enargite but Luzonit Famatinit and crystallize in the tetragonal crystal system. Enargite can contain a maximum of about 20 % antimony, with larger contents always results Famatinit.
There are two known varieties of Enargits. Of these contains a silver, the other tin.
A 1957 Strunz described and designated as Stibioenargit mineral was not recognized by the IMA (founded 1959), but is classified as possible antimony-containing variety of enargite or hypothetical orthorhombic polymorph of Famatinit.
Education and Locations
Enargite formed under hydrothermal conditions at temperatures of 280-600 ° C. He is often associated with pyrite, sphalerite, galena, bornite, tetrahedrite, tennantite, chalcocite, covellite, barite and quartz.
Worldwide, enargite so far (as of 2011) are detected at around 740 localities. Apart from its type locality Morococha in the region of Junín, where the largest Enargitkristalle with up to 15 cm in length came to light, the mineral still found in many other regions of Peru. Noteworthy due to its outstanding Enargitfunde is also the also located in Peru " Luz Angelica Mine " at Quiruvilca (Santiago de Chuco ) in the region of La Libertad with crystal finds to about 10 cm in size.
In Europe, we find the mineral, for example 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 located in the Andes of South America, mainly in Peru, Chile and Argentina. But even in the United States (Montana, Utah, Arizona, Colorado), Luzon (Philippines ), and Japan are known occurrences.
Crystal structure
Enargite crystallizes in the orthorhombic crystal system, space group Pnm21 ( Raumgruppen-Nr. 31) with the lattice parameters a = 6.44 Å, b = 7.41 Å and c = 6.15 Å and two formula units per unit cell.
Use
Enargite is an important raw material for the extraction of copper.