Umangite
Umangit is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts " (including selenides, tellurides, arsenides, antimonides and bismuthides ). It crystallizes in the tetragonal crystal system with the idealized chemical composition Cu3Se2 and is therefore chemically seen a copper selenide. For natural Umangiten however, a portion of the copper with silver (Ag ) may be replaced with silver contents were measured to about 0.5% in the various analyzes.
Umangit is opaque and is found exclusively in the form of granular to massive mineral aggregates. Occasionally, a flashy, lamellar twinning can be observed. Fresh samples are of dark cherry-red, purplish -playing color and have a metallic luster. Weathering the mineral, however, proceeds rapidly dark purple to blue- black to become dull.
With a Mohs hardness of 3 Umangit belongs to the medium-hard minerals that can be similar to the reference mineral calcite scratch with a copper coin.
Etymology and history
Was first discovered in the Sierra de Umangit Umango in the Argentine province of La Rioja and described in 1891 by Frederick Klock man who named the mineral after its type locality.
Classification
In the outdated, but partly still in use 8th edition of the mineral classification by Strunz the Umangit belonged to the department of " sulfides, selenides and tellurides with the molar ratio of metal: S, Se, Te > 1: 1", where he along with Athabascait, Bellidoit, Berzelianit, Crookesit and Sabatierit the unnamed group II/B.03 formed.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Umangit also in the department of " metal sulfides with the molar ratio M: S> 1: 1 ( mainly 2: 1) " a. However, this is further divided according to the conditions prevailing in the interconnect metals, so that the mineral according to its composition in the subsection " copper (Cu), silver (Ag ) and / or gold (Au) " can be found, where it is the only Member forms the unnamed group 2.BA.15c.
The mainly common in English-speaking classification of minerals according to Dana assigns the Umangit into the class of " sulfides and sulfosalts " and there in the department of " sulfide minerals ." Here he is the only member / along with the unnamed group 02:05:01 within the subdivision " sulfides - tellurides and selenides, including - with the composition AmBnXp, with (m n): p = 3: 2" to find.
Education and Locations
Umangit be hydrothermally formed at below 112 ° C in veins, where he mostly in paragenesis with other selenides such as, but Berzelianit, Clausthalite, Eukairit, Guanajuatit, Klockmannit, Naumannite and Tiemannit, but also with other sulfide minerals such as Chalkomenit, chalcopyrite, cobaltite, hessite and pyrite as well as the carbonates calcite and malachite occurs.
A rare mineral formation Umangit could be detected only in a few localities, where so far (as of 2014) are about 70 localities known as. Apart from its type locality Sierra de Umango the mineral still occurred in Argentina in different places in the Sierra de Cacho in Puerto Alegre in the department of Famatina and the District Sañogasta in the province of La Rioja, as well as belonging to the province of Mendoza Sierra de Cacheuta on.
In Germany they found Umangit among others in the Clara mine in Oberwolfach and the former uranium deposit in the pit Krunkelbach Menzenschwand in Baden- Württemberg; in the " pit Christa" in Großschloppen in the Fichtelgebirge mountains in Fluoritbergbaugebiet at Wölsendorf in Bavaria; the pits " Brummerjan " in Zorge, " bunch of grapes " at Lerbach ( Osterode am Harz ), " Red Bear " and " Wennsglückt " at St. Andrew Berg and in the quarry glaciated valley at Lautenthal in Lower Saxony; in a greywacke quarry at Rieder ( Ballenstedt ) and Tilkerode - Abberode in Saxony- Anhalt, in Schlema - Hartenstein District in the Saxon Erzgebirge and open pit Lichtenberg at Ronneburg in Thuringia.
The only known locality in Austria is a Selenidvorkommen on Eselsberg at Altenberg an der Rax in Styria.
Other localities lie including Australia, Bolivia, China, the Democratic Republic of Congo ( Zaire ), France, Canada, Greenland, Mexico, Namibia, Poland, Russia, Sweden, the Czech Republic, the United Kingdom ( England) and the United States of America (Colorado, Washington).
Crystal structure
Umangit crystallized tetragonal in the space group P421m ( Raumgruppen-Nr. 113) with the lattice parameters a = 6.40 Å and c = 4.28 Å and two formula units per unit cell.