{{Short description|Sulfide mineral}} {{infobox mineral |name = Tetradymite | category = Sulfide mineral | boxwidth = | boxbgcolor = | image = Tetradymite.jpg | caption = Tetradymite - British Columbia, Canada | imagesize = 260px | formula = Bi<sub>2</sub>Te<sub>2</sub>S | IMAsymbol = Ttd<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = | strunz = 2.DC.05c | dana = 02.11.07.01 | system = Trigonal | class = Hexagonal scalenohedral ({{overline|3}}m) <br/>H-M symbol: ({{overline|3}} 2/m) | symmetry = ''R''{{overline|3}}m | color = Steel-gray with dull to iridescent tarnish; white in polished section | colour = | habit = Pyramidal prisms, commonly granular, massive to foliated, also bladed | twinning = Twin planes {0118} and {0115} | cleavage = Perfect on {0001} | fracture = Uneven | tenacity = Laminae flexible, slightly sectile. | mohs = 1.5{{snd}}2 | luster = Metallic, splendent on fresh surfaces, dull if tarnished | streak = Steel-gray | diaphaneity = Opaque | gravity = 7.2{{snd}}7.9 | density = | polish = | opticalprop = | refractive = | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = | alteration = | references = <ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Tetradymite Mineralienatlas]</ref><ref name=Handbook>http://rruff.geo.arizona.edu/doclib/hom/tetradymite.pdf Handbook of Mineralogy</ref><ref name=Webmin>http://webmineral.com/data/Tetradymite.shtml Webmineral data</ref><ref name=Mindat>http://www.mindat.org/min-3921.html Mindat.org</ref> }}
'''Tetradymite''' is a mineral consisting of bismuth, tellurium and sulfide, Bi<sub>2</sub>Te<sub>2</sub>S, also known as telluric bismuth. If sulfur is absent the mineral is tellurobismuthite and the formula is then Bi<sub>2</sub>Te<sub>3</sub>. Traces of selenium are usually present.{{sfn|Spencer|1911}} left|thumb|180px|A sample of tetradymite Crystals are rhombohedral, 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 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 = 1.5{{snd}}2) and marks paper. The specific gravity is 7.2 to 7.9.{{sfn|Spencer|1911}}
The type locality is Zupkov (Zsubko; Schubkau), Stredoslovenský Kraj, Slovak Republic where it was reported in 1831.<ref name=Mindat/> It was first found, in 1815, at Telemark in Norway.{{sfn|Spencer|1911}} It often occurs in high temperature hydrothermal quartz veins associated with native gold and in contact metamorphic deposits.<ref name=Handbook/>
==References== {{Reflist}}
'''Attribution:'''
==External links== {{Commons category}} {{EB1911|wstitle=Tetradymite|volume=26|page=670|first=Leonard James|last=Spencer|authorlink=Leonard James Spencer}}
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Category:Bismuth minerals Category:Telluride minerals Category:Sulfide minerals Category:Tetradymite group Category:Trigonal minerals Category:Glances Category:Minerals in space group 166 Category:Minerals described in 1831