Argyrodite

Argyrodite is a very rarely occurring mineral from the mineral class of " sulfides and sulfosalts ." It crystallizes in the orthorhombic crystal system with the chemical composition and Ag8GeS6 developed to 18 cm large crystals with a pseudo- octahedral, dodekaedrischem, cubic habit, or combinations of these forms. Also in radialstrahligen, nierigen or massive mineral aggregates and crusty coatings can occur.

Argyrodite forms with Canfieldit ( Ag8SnS6 ) a solid solution series.

Special Features

Argyrodite containing about 74 % silver, 6.0% Ge, 17 % sulfur, as well as admixtures of iron (0.7%), zinc (0.2%) and traces of mercury.

In fresh state, argyrodite shows in steel gray color with reddish to purple shimmer and metallic luster. However, the crystal faces running after some time on black.

When heated in closed-end glass tube, it provides a glossy black sublimate, in the open tube sulphurous acid, however: on coal finally melts it to the ball, and the white citrongelbe fittings supplies last and leaves behind a silver grain.

Etymology and history

Named after the Greek word argyrodite άργνρώδης ( = silver containing ) based on its high silver content. The mineral was in 1886 by Albin Weisbach ( 1833-1901 ) discovered and described on the Himmelsfürst -mine near Freiberg ..

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the argyrodite belonged to the mineral class of " sulfides and sulfosalts " and then to the Department of " sulfides with the molar ratio of metal: sulfur, selenium, tellurium > 1:1", where he formed a distinct group with Canfieldit and Putzit.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the argyrodite in the class of " sulfides and sulfosalts " and there in the department of "Metal Sulfides, M: S> 1: 1 ( mainly 2: 1) " a. This division, however, is further subdivided according to the nature of the cations involved, so that the mineral according to its composition in the subdivision " with copper ( Cu), silver (Ag ) and / or gold ( Au) " is to find where it continues to is present together with Canfieldit and Putzit the unnamed group 2.BA.35.

The classification of minerals according to Dana assigns the argyrodite in the class of " sulfides and sulfosalts " and there in the department of " sulfide minerals ." Here he is named the " Argyroditgruppe " with the system no. To find | 2:05:06 and the other member within the subdivision "[] [ classification of minerals according to Dana / # ] ".

Education and Locations

Argyrodite consists predominantly at relatively low temperatures from hydrothermal solutions in deposits with base metals from. It is accompanied, among others, chalcopyrite, galena, pyrite, siderite, sphalerite, stephanite and various silver sulfosalts.

Worldwide argyrodite could be detected in about 50 localities. Another locality in Germany in addition to its type locality Himmelsfürst is still also located at Brand-Erbisdorf "United box Mine" and " brings happiness Mine" with train ( Freiberg ) in Saxony and the Hornbühl in Waldkirch in Baden- Württemberg known.

Other localities include in Jujuy and La Rioja in Argentina, New South Wales in Australia, Oruro and Potosí in Bolivia, the provinces of Fujian and Hubei in China, Auvergne, Limousin and Provence- Alpes -Cote d' Azur in France, the County Tipperary in Ireland, Hokkaido and Honshu in Japan, Souss -Massa -Draa in Morocco, Guanajuato in Mexico, the North Island of New Zealand, Alba, Romania, the Far Eastern Federal District in Russia, Prešov in Slovakia, Castile -La Mancha in Spain, Värmland in Sweden, as well as Alaska, Colorado, Nevada, and Utah in the United States.

Crystal structure

Argyrodite crystallizes in the orthorhombic space group Pna21 with the lattice parameters a = 15.15 Å; b = 7.48 Å and c = 10.59 Å and four formula units per unit cell.