Tetradymite is a

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

consisting of

bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...

tellurium Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionall ...

and sulfide, Bi₂ Te₂ S, also known as telluric bismuth. If sulfur is absent the mineral is

tellurobismuthite Tellurobismuthite, or tellurbismuth, is a telluride mineral: bismuth telluride (bismuth, Bi2tellurium, Te3). It crystallizes in the trigonal system. There are natural cleavage planes in the (0001) direction as the crystal is effectively lamellar (l ...

and the formula is then Bi₂Te₃. Traces of

selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...

are usually present. Crystals are

rhombohedral In geometry, a rhombohedron (also called a rhombic hexahedron or, inaccurately, a rhomboid) is a three-dimensional figure with six faces which are rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be us ...

, but are rarely distinctly developed; they are twinned together in groups of four; hence the name of the mineral, from the Greek for fourfold. There is a perfect cleavage parallel to the

basal plane In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns t ...

and the mineral usually occurs in foliated masses of irregular outline. The color is steel-gray, and the luster metallic and brilliant. The mineral is very soft (H = 1.52) and marks paper. The specific gravity is 7.2 to 7.9. The type locality is Zupkov (Zsubko; Schubkau), Stredoslovenský Kraj, Slovak Republic where it was reported in 1831. It was first found, in 1815, at

Telemark Telemark is a traditional region, a former county, and a current electoral district in southern Norway. In 2020, Telemark merged with the former county of Vestfold to form the county of Vestfold og Telemark. Telemark borders the traditional ...

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...

. It often occurs in high temperature

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...

associated with native

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...

and in

contact metamorphic Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of che ...

deposits.

References

Attribution: *

External links

{{Commons category Bismuth minerals Telluride minerals Sulfide minerals Tetradymite group Trigonal minerals Minerals in space group 166