Tetradymite
| Tetradymite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Bi 2 Te 2 S |
|
Mineral class (and possibly department) |
Sulfides and sulfosalts |
|
System no. to Strunz and to Dana |
2.DC.05 ( 8th edition : II / D.09) 02.11.07.01 |
| Crystallographic Data | |
| Crystal system | trigonal |
| Crystal class ; symbol | ditrigonal-scalenohedral 3 2 / m 1 |
| Space group | R 3 m |
| Lattice parameters | a = 4.24 Å ; c = 29.59 Å |
| Formula units | Z = 3 |
| Physical Properties | |
| Mohs hardness | 1.5 to 2 |
| Density (g / cm 3 ) | 7.3 |
| Cleavage | completely after {0001} |
| Break ; Tenacity | uneven |
| colour | tin white to light steel gray, often tinged with variegated colors |
| Line color | light steel gray |
| transparency | opaque |
| shine | Metallic luster |
| Other properties | |
| Chemical behavior | soluble in nitric acid HNO 3 and sulfuric acid H 2 SO 4 |
Tetradymite is a seldom occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the trigonal crystal system with the chemical composition Bi 2 Te 2 S and develops mostly millimeter to centimeter-sized, pyramidal crystals in characteristic crystal twins and quadruplets, but also leafy to massive mineral aggregates from pewter-white to light steel-gray in color, which often become brightly colored.
Etymology and history
Was first discovered in 1831 at tetradymite Župkov in bird mountains described by Slovakia and Haidinger , the mineral from the Greek word tetradymos (Quad) named.
classification
In the meantime outdated 8th edition of Strunz'schen systematic mineral of tetradymite is part of the department of "sulfides and sulfosalts with the molar ratio of metal: sulfur, selenium, tellurium <1: 1", where he together with Kawazulith , Paraguanajuatit , Skippenit , Tellurantimon and Tellurobismutite forms its own group.
Since the 9th edition of Strunz's systematics of minerals , which was revised in 2001 , the class of sulfides and sulfosalts has been expanded to include selenides, tellurides, arsenides, antimonides, bismuthides, sulfarsenites, sulfantimonites and sulfbismuthites, and partly more finely divided according to type the cations involved in the compound. The tetradymite is thus now in the Department of "metal sulfides with M: S = 3: 4 and 2: 3" to find wherein the mineral together with Aleksit , Babkinit , Baksanit , Hedleyit , Ikunolit , Ingodit , Joseit-A , Joséit- B , Joseit-C , Kawazulit , Kochkarit , Laitakarit , Nevskit , Paraguanajuatit , Pilsenit , Poubait , Protojoseit , Rucklidgeit , Saddlebackit , Skippenit , Sulphotsumoit , Sztrókayit , Tellurantimon , Tellurobismutit , Telluronevskit , Tsumoit and Vihorlatit in the subsection "variable molar ratio of M : S “stands.
The systematics of minerals according to Dana , which is common in the English-speaking world , also assigns the tetradymite to the class of sulfides, but there in the division of “sulfides - including selenides and tellurides - with the (general) composition A m B n X p , with (m + n): p = 2: 3 ". As a lead mineral, it forms the subdivision "2.11.7 Tetradymite group (Trigonal:) " together with tellurium bismuthite, tellurium antimony, paraguanajuatite, kawazulite and skippenite
Education and Locations
Tetradymite is mostly formed by hydrothermal processes in medium to high grade gold deposits , but also by contact metamorphism . There it occurs in paragenesis with solid gold , silver , tellurium , hessite , petzite , pyrite , galena and sphalerite .
Tetradymite has been detected at around 330 sites worldwide so far (as of 2010), including in Argentina , Armenia , Australia , Belgium , Bolivia , Brazil , Bulgaria , China , Germany , Finland , France , Greece , Japan , Canada , Kazakhstan , Mexico , New Zealand , Norway , Austria , Poland , Romania , Russia , Sweden , Switzerland , Serbia , Zimbabwe , Slovakia , Spain , South Africa , Tanzania , Turkey , Czech Republic , Ukraine , Hungary , United Kingdom (Great Britain) and the United States of America .
Crystal structure
Tetradymite crystallizes trigonal in the space group with the lattice parameters a = 4.24 Å and c = 29.59 Å as well as three formula units per unit cell .
See also
Individual evidence
- ↑ a b Webmineral - Tetradymite (English)
- ^ A b 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. 98 .
- ↑ a b Handbook of Mineralogy - Tetradymite (English, PDF 61.2 kB)
- ↑ Mindat - Localities for Tetradymite
- ^ 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. 98 .
Web links
- Mineral Atlas: Tetradymite (Wiki)