Freibergite

• Silberfahlerz
• Weißgiltigerz

Freibergite is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts ." It crystallizes in a cubic crystal system having the idealized chemical composition Ag6 [ Cu4Fe2 ] Sb4S13 -x, and is therefore a silver - copper-iron Sulfoantimonid.

Since naturally entstandenem Freibergite usually a small proportion of silver with copper or a part of the iron with zinc and a part of the antimony is replaced by arsenic diadoch ( substituted ) and in order to clarify the weaving structure of the chemical components, the chemical composition of the mineral as a mixed crystal of the formula in the form of chemical structural formula ( Ag, Cu ) 10 ( Fe, Zn ) 2 [ S | ( (Sb, As) S3 ) 4] given. The items shown in the parentheses can be represented each other in the formula, but are always in the same proportions to the other components of the mineral.

Freibergite in any form is opaque (opaque ), and is usually found in other minerals, but also develops euhedral, tetrahedral crystals to about 3.5 inches in size and metallic luster in the form of massive mineral aggregates and inclusions. Its color is steel gray to black and its stroke color reddish black.

Etymology and history

Silver-bearing tetrahedrite or " Weißgültigerz " (also Weissgültigerz or Weissgiltigerz ), which include the Freibergite matters is already known early in the mine essence and delivered in writing at least since 1562 by Johannes Mathesius ( Sarepta or mountain Piety ). That the silver-bearing tetrahedrite consists of various minerals, was revealed by chemical analysis only in 1795 by Martin Heinrich Klaproth in 1829 by Heinrich Rose, which were carried out at various mineral samples from the Freiberg district.

Klaproth in 1795 led its chemical analysis on a quantitative basis in mineral samples from the Himmelsfürst mine at Brand-Erbisdorf by. Based on the results, after which the samples had two very different levels of silver with an average of 22.00 % and 9.41%, he introduced the distinction between sparse (silver -rich) and dark ( Braqo de Prata ) Weißgültigerz. As in his samples but one end was missing copper and on the other hand, a considerably higher lead content of 40 to 50 % was included, it can be assumed that Klaproth mixture has investigated instead of pure minerals. Rose analyzed in 1829, however, well-trained and very silver-rich tetrahedrite crystals, the ( " brings luck" later) had been found at Freiberg three years earlier in the "Have Eight treasure trove ". In addition to the expected high silver content of 31.29 %, he found in his sample this time also significant for Freibergite copper content of 14.81 %. Other samples from the New Hope God treasure trove at Bräunsdorf ( Oberschona ), the archangel Michael Erbstollen at Mohorn and from Old Woischitz in Bohemia had a silver content of 29.43 to 32.69 %.

Based on the analysis of Rose finally wrote Carl Gustav Adalbert von Weissenbach 1831 Mineral Freibergite under the names " Weißgiltigerz " or "True Frey Berger Weißgiltigerz " as a separate mineral. His final name was Freibergite but only in 1853 by Gustav Adolf Kenngott, who named the mineral after its type locality.

Meanwhile chose Ernst Friedrich Glocker (1847 ) for the " light Weißgültigerz " the generic name Polytelit (from Greek politelos for costly ) based on its high silver content and especially for the clear Weißgültigerze from Freiberg the species name Polytelites Fribergensis or free Bergischer Polytelit. Glockers names but not prevailed.

Classification

In the outdated, but partly still in use 8th edition of the mineral classification by Strunz the Freibergite 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 collaborated with Argentotennantit, Chaméanit, Giraudit, Goldfieldit, Hakit, Mgriit, tennantite and tetrahedrite the " tetrahedrite - group " with the system no. II/C.11 formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Freibergite also in the class of " sulfides and sulfosalts ," there, however, in the department of " Sulfoarsenide, Sulfoantimonide, Sulfobismuthide ". This is also further divided according to the link type of the connection components, so that the mineral according to the division of the " island ( Neso ) Sulfarsenide etc., with additional sulfur ( S) " is to find where it together with Argentotennantit, Argentotetraedrit, Galkhait, Giraudit, Goldfieldit, Hakit, tennantite and tetrahedrite the " Tennantitgruppe " with the system no. 2.GB.05 forms.

The classification of minerals according to Dana assigns the Freibergite in the class of " sulfides and sulfosalts " and there in the department of " thio " one. Here he is with tetrahedrite, tennantite, Hakit, Giraudit, Goldfieldit and Argentotennantit in the " Tetraedritgruppe " with the system no. 03:03:06 found within the sub-division of " sulfosalts with the ratio 3 < z / y < 4 and the composition (A ) i ( A2 ) j [ Bycz ], A ​​= metals, B = semimetals, C = non-metals ".

Education and Locations

Freibergite like all tetrahedrite is mainly in hydrothermal deposits. In addition, however, it can also occur in subordinate pegmatitic - pneumatolytic deposits and sedimentary rocks. Accompanying minerals, in addition to tennantite and tetrahedrite many different sulfides and sulfosalts occur such as, but arsenopyrite, Bournonite, chalcopyrite, galena, pyrite and sphalerite.

As a rather rare mineral formation Freibergite at different sites can indeed be abundant in some cases, overall it is not very common. Total so far (as of 2013) are slightly more than 600 localities known as. Apart from its type locality Freiberg or generally in the Freiberg mining district - rich, massive deposits is known primarily from the Himmelsfürst treasure trove - in the Saxon Erzgebirge, the mineral occurred in Germany, among others, still Hornbühl in Waldkirch in Haslach and Belchenhotel in Baden- Württemberg; in the pit " Silver Rose " in Goldkronach fire wood and the Prince colliery at Lam in Bavaria; the " mine Rammelsberg " at Goslar in Lower Saxony; on Moschellandsberg and Fischbacher plant in Rhineland-Palatinate and in Neudorf and Strassberg ( Harzgerode ) in Saxony- Anhalt.

In Austria Freibergite was mainly in the Hohe Tauern Carinthia found to Salzburg, so among other things, in the Goldberg, Hafner and Kreuzeckgruppe, but also in Rotgülden in the region of Lungau (Salzburg), Kaltenegg (municipality Rettenegg ) and Arzberb ( Weiz ) are found in Styria, near Schwaz in Tyrol.

The only known locality in Switzerland is the Val Minor in the canton of Grisons.

Other localities lie among other things in Egypt, Argentina, Azerbaijan, Australia, Bolivia, Brazil, Bulgaria, Chile, China, Ecuador, Finland, France, Georgia, Ghana, Greece, Greenland, India, Ireland, Italy, Japan, Canada, Kazakhstan, Colombia, Kosovo, Morocco, Macedonia, Mexico, Mongolia, Norway, Papua New Guinea, Peru, Poland, Portugal, Romania, Russia, Sweden, Serbia, Slovakia, Slovenia, Spain, South Korea, Tajikistan, Czech Republic, Tunisia Turkey, Ukraine, Hungary, the United Kingdom ( UK) and the United States of America (USA).

Crystal structure

Freibergite crystallized cubic space group I43m ( Raumgruppen-Nr. 217 ) with the lattice parameters a = 10.61 Å and two formula units per unit cell.

Use

Freibergite was an important ore for the extraction of copper and silver in addition to other local accumulation Fahl ores. The latter is now primarily obtained from argentiferous galena.