Stephanite
- Sprödglaserz
- Sprödglanzerz
- Schwarzgültigerz
- Crystal chemical structural formula: Ag5 [ S | SbS3 ]
- Molecular Formula: Ag5SbS4
- Oxide formula: 5 Ag2S · Sb2S3
Stephanite, also known as Sprödglaserz, Sprödglanzerz and Schwarzgültigerz, is a mineral from the mineral class of " sulfides and sulfosalts ," which abound in various localities in part, but overall is not widespread. It crystallizes in the orthorhombic crystal system with the composition Ag5 [ S | SbS3 ], and is therefore chemically saw a silver -antimony sulpho salt.
Stephanite usually develops short prismatic to acicular crystals and longitudinally striped, but also rosette- and step-shaped or bulky mineral aggregates of lead- gray to iron- black color with black stroke color. In air, it runs occasionally on matte black or colorful color. The surfaces of fresh samples exhibit a metallic luster.
Special Features
Before the blowpipe on charcoal stephanite is first cracked and then melts to give a fitting of antimony (III ) oxide forms. With soda melted a silver grain forms. Of diluted nitric acid is decomposed stephanite to precipitate sulfur, and antimony ( III) oxide.
Etymology and history
Stephanite was already known to the miners in the Middle Ages as a rich silver ore, but under the names Sprödglaserz and Rösch plant ( Middle High German for fresh, hard, brittle or crunchy, crispy ) as opposed to soft green, now silver gloss or acanthite. The term Sprödglaserz also took Abraham Gottlob Werner ( 1789) in his mineralogical records. By sound shift but still transformed into Werner times " glass " to " shine ", so can be found among others at Friedrich Hausmann's Manual of Mineralogy (1813 ) the name Sprödglanzerz. Occasionally, were also Schwarzgültigerz, Schwarzgülden or rare Schwarzerz in line with the often black color of the Stephanits in circulation.
The final name of stephanite received the mineral in 1845 by Wilhelm Ritter von Haidinger, which it in honor of Archduke Stephan of Austria, named after this.
As a type locality applies the Freiberg mining district in Saxony.
Classification
Already in the now outdated but still in use 8th edition of the mineral classification by Strunz was one of stephanite to the mineral class of " sulfides and sulfosalts " and then to the Department of " thio " where he along with Arcubisit, Fettelit and Selenostephanit the unnamed group II / E.06 formed.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the stephanite also in the class of " sulfides and sulfosalts ," there, however, in the newly defined division of " Sulfoarsenide, Sulfoantimonide, Sulfobismuthide " a. This division is also subdivided in accordance with the crystal structure and of the possible Anweisenheit additional sulfur into the formula so that the mineral according to its structure and its composition, in the subsection " island ( neso ) Sulfarsenide etc., with additional sulfur (S) " to is find out where it. sold with Selenostephanit named after him " Stephanitgruppe " with the system no 2.GB.10 forms.
The mainly common in English-speaking classification of minerals according to Dana assigns the stephanite in the class of " sulfides and sulfosalts " and there in the department of " thio " one. Here he is with Selenostephanit in the named also after him " Stephanitgruppe " with the system no. 03:02:04 within the sub-division of " sulfosalts with the ratio z / y = 4 and the composition (A ) i ( A2 ) j [ Bycz ], A = metals, semimetals B =, C = non-metals " to be found.
Education and Locations
Stephanite is formed hydrothermally in geologically active ( recent ) fault zones of the earth's crust. There it is, especially in silver deposits, accompanied by acanthite, galena, to find native silver, Proustite, pyrite, sphalerite and tetrahedrite.
Worldwide, so far (as of 2012) about 500 localities for stephanite known. Apart from its type locality Freiberg where the mineral became evident in many mines in the area, it was in Germany, among others, yet in several mines in Annaberg -Buchholz, Johann George Town, Marienberg, Baerenstein and Schneeberg in Saxony and in many other places in Baden- Württemberg Bavaria, Hesse, North Rhine -Westphalia and Lower Saxony be found.
In Austria, stephanite found in some localities in Carinthia, Salzburg and Styria and Switzerland are only a few localities in the canton of Valais ( Binn Valley, Loetschental, Martigny ) known.
Known due to exceptional Stephanitfunde with crystals of several centimeters in size include Pribram ( German: Příbram, older even Freiberg in Bohemia) and Jáchymov ( German Jáchymov ) in the Czech Republic and the Sparky mine at Arizpe, Sonora, Mexico.
Other localities lie among others in Argentina, Australia, Bolivia, Bulgaria, Chile, China, Ecuador, France, Greece, Honduras, India, Italy, Japan, Kazakhstan, Colombia, Morocco, Norway, Peru, the Philippines, Poland, Portugal, Romania, Russia, Sweden, Slovakia, Spain, Tajikistan, Hungary, Uzbekistan, the United Kingdom ( UK) and the United States of America (USA).
Crystal structure
Stephanite crystallizes in the orthorhombic crystal system, space group Cmc21 ( Raumgruppen-Nr. 36) with the lattice parameters a = 7.84 Å; b = 12.47 Å and c = 8.54 Å and four formula units per unit cell.
Use
Due to the silver content of up to 68% is an important stephanite silver ore.