Freibergite
| Freibergite | |
|---|---|
 |
|
| General and classification | |
| other names |
|
| chemical formula | Ag 6 [Cu 4 Fe 2 ] Sb 4 S 13-x |
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.GB.05 ( 8th edition : II / C.11) 03.03.06 |
| Crystallographic Data | |
| Crystal system | cubic |
| Crystal class ; symbol | cubic-hexakistrahedral; 4 3 m |
| Room group (no.) | I 4 3 m (No. 217) |
| Lattice parameters | a = 10.61 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 3.5 to 4 |
| Density (g / cm 3 ) | 5.41 |
| Cleavage | no |
| Break ; Tenacity | uneven to scalloped |
| colour | steel gray to black |
| Line color | reddish black |
| transparency | opaque |
| shine | Metallic luster |
Freibergite is a rather seldom occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the cubic crystal system with the idealized chemical composition Ag 6 [Cu 4 Fe 2 ] Sb 4 S 13-x , so it is a silver - copper - iron - sulfoantimonide .
Since in naturally formed Freibergite a small proportion of the silver is usually replaced ( substituted ) by copper or part of the iron by zinc and part of the antimony by arsenic and in order to clarify the bond structure of the chemical components, the chemical composition of the mineral also given as a mixed formula in the form of the crystal chemical structural formula (Ag, Cu) 10 (Fe, Zn) 2 [S | ((Sb, As) S 3 ) 4 ]. The elements indicated in round brackets can represent each other in the formula, but are always in the same proportion to the other components of the mineral.
Freibergite is opaque in every form and is mostly found in the form of massive mineral aggregates and inclusions in other minerals, but also develops idiomorphic , tetrahedral crystals up to about 3.5 centimeters in size and metallic luster . Its color is steel gray to black and its line color is reddish black.
Etymology and history
Silver-bearing tetrahedrite or "Weißgültigerz" (also Weissgültigerz or Weissgiltigerz ), including the Freibergit matters is in the mine being early known and writing at least since 1562 by Johannes Mathesius ( Sarepta or mountain Postille handed). The fact that the silver-bearing pale ore consists of various minerals was first discovered in 1795 by Martin Heinrich Klaproth and in 1829 by Heinrich Rose through chemical analyzes carried out on various mineral samples from the Freiberg mining area.
In 1795 Klaproth carried out his chemical analysis on a quantitative basis on mineral samples from the Himmelsfürst treasure trove near Brand-Erbisdorf . On the basis of the results, according to which the samples had two very different silver contents with an average of 22.00% and 9.41%, respectively, he introduced the distinction between light (rich in silver) and dark (poor in silver) white gold ore. However, since his samples lacked copper on the one hand and contained a conspicuously high lead content of 40 to 50% on the other, one can assume that Klaproth examined mixtures instead of pure minerals. In 1829 Rose, on the other hand, analyzed well-developed and very silver-rich pale ore crystals that had been found three years earlier in the “Hab Acht Fundgrube” (later “Beschert Glück”) near Freiberg . In addition to the expected high silver content of 31.29%, this time he also found the copper content of 14.81%, which is significant for Freibergite, in his samples. Further samples from the New Hope God's treasure trove near Bräunsdorf (Oberschöna) , the Archangel Michael Erbstollen near Mohorn and from Alt Woischitz in Bohemia showed a silver content between 29.43 and 32.69%.
On the basis of Rose's analyzes, Karl Gustav Adalbert von Weissenbach finally described the mineral Freibergite in 1831 under the designation "Weißgiltigerz" or "True Freyberger Weißgiltigerz" as an independent mineral. However, Freibergit was given its name, which is still valid today, in 1853 from Gustav Adolf Kenngott , who named the mineral after its type locality .
In the meantime, Ernst Friedrich Glocker (1847) chose the generic name polytelite (from the Greek politelos for costly ) for the “light white gold ore” based on its high silver content and especially for the light white gold ore from Freiberg the species name Polytelites Fribergensis or Freibergischer polytelite . However, Glocker's names did not catch on.
classification
In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , Freibergite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with a molar ratio of metal: sulfur (selenium, tellurium) = 1: 1", where together with argentotennantite , chaméanite , giraudite , goldfieldite , hakit , mgriit , tennantite and tetrahedrite the "tetrahedrite group" with the system no. II / C.11 formed.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns Freibergite to the class of "sulfides and sulfosalts", but in the department of "sulfoarsenides, sulfoantimonides, sulfobismuthides". This is further subdivided according to the type of linkage of the compound components, so that the mineral can be found in the subdivision of "island sulfarsenides (Neso-sulfarsenides) etc., with additional sulfur (S)", where it can be found together with argentotennantite, argentotetraedrite , Galkhait , Giraudit, Goldfieldit, Hakit, Tennantit and Tetrahedrite the "Tennantitgruppe" with the system no. 2.GB.05 forms.
The systematics of minerals according to Dana also assigns Freibergite to the class of "sulfides and sulfosalts" and there in the department of "sulfosalts". Here it is together with tetrahedrite, tennantite, hakite, giraudite, goldfieldite and argentotennantite in the "tetrahedrite group" with the system no. 03.03.06 within the subdivision of " Sulphosalts with the ratio 3 <z / y <4 and the composition (A +) i (A2 +) j [ByCz], A = metals, B = semi-metals, C = non-metals ".
Education and Locations
Freibergite, like all Fahl ores, is mainly formed in hydrothermal deposits . In addition, it can also arise subordinately in pegmatitic - pneumatolytic deposits and sedimentary rocks . In addition to tennantite and tetrahedrite, many different sulfides and sulfosalts can occur as accompanying minerals , such as arsenopyrite , bournonite , chalcopyrite , galena , pyrite and sphalerite .
As a rather rare mineral formation, Freibergite can sometimes be abundant at various sites, but overall it is not very widespread. In total, a little more than 600 sites are known to date (as of 2013). In addition to its type locality Freiberg or in general in the Freiberg mountain area - rich, massive deposits are known mainly from the Himmelsfürst treasure trove - in the Saxon Ore Mountains, the mineral occurred in Germany, among others, at Hornbühl near Waldkirch , near Haslach in Kinzigtal and Belchen in Baden-Württemberg ; in the “Silver Rose” mine near Goldkronach- Brandholz and the Fürstenzeche near Lam in Bavaria; the "Rammelsberg mine" near Goslar in Lower Saxony; at the Moschellandsberg and in the Fischbacher plant in Rhineland-Palatinate as well as at Neudorf and Straßberg (Harzgerode) in Saxony-Anhalt.
In Austria, Freibergite was found primarily in the Hohe Tauern from Carinthia to Salzburg, including in the Goldberg , Hafner and Kreuzeck groups , but also near Rotgülden in the Lungau (Salzburg), Kaltenegg ( Rettenegg municipality ) and Arzberb (Weiz ) regions ) can be found in Styria and near Schwaz in Tyrol.
The only known site in Switzerland so far is the Val Minor in the canton of Graubünden.
Other locations are 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 crystallizes cubically in the space group I 4 3 m (space group no. 217) with the lattice parameter a = 10.61 Å and two formula units per unit cell .
use
When locally accumulated, Freibergite was an important ore for the extraction of copper and silver, along with other pale ores . The latter is now primarily obtained from silver-containing galena .
See also
literature
- MH Klaproth : Investigation of the silver ores. 5th section. White validity ore. In: Contributions to the chemical knowledge of mineral bodies. Volume 1 (1795), pp. 166-177
- H. Rose : About the naturally occurring non-oxidized compounds of antimony and arsenic. In: Poggendorffs Annalen der Physik und Chemie (1829), Volume 91 (or 15), pp. 573-591
- A. Kenngott : Freibergit , In: The Mohs'sche Mineralsystem, edited according to the current standpoint of science , published and printed by Carl Gerold & Sohn, Vienna 1853, pp. 117–117 ( PDF 783.4 kB )
- Freibergite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 61.3 kB )
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 435 (first edition: 1891).
- Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 174-175 .
Web links
- Mineral Atlas: Freibergite (Wiki)
- Thomas Witzke : The discovery of Freibergite (accessed September 27, 2013)
- Webmineral - Freibergite
- American-Mineralogist-Crystal-Structure-Database - Freibergite
Individual evidence
- ↑ a b A. Kenngott : Freibergit , In: The Mohs'sche Mineralsystem, edited according to the current standpoint of science , published and printed by Carl Gerold & Sohn, Vienna 1853, pp. 117–117 ( PDF 783.4 kB )
- ↑ a b IMA / CNMNC List of Mineral Names; August 2013 (PDF 1.3 MB)
- ↑ a b c d Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 122 .
- ^ Mindat - Freibergite
- ↑ a b Thomas Witzke : The discovery of Freibergite (accessed on September 27, 2013)
- ↑ CGA Weissenbach: About the content of silver ores occurring in Saxon mining. In: Calendar for the Saxon miner and hut man to the year 1831 , pp. 233–248
- ↑ Mindat - Number of localities for Freibergite
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 ( Dörfler Natur ).
- ↑ List of localities for Freibergite in the Mineralienatlas and Mindat
- ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 175 .