- Tetradymite
Tetradymite is a
mineral consisting ofbismuth ,tellurium and sulfide, Bi2Te2S, also known as telluric bismuth. Ifsulfur is absent the mineral is tellurobismuthite and the formula is then Bi2Te3. Traces ofselenium are usually present.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-grey, and the lustre metallic and brilliant. The mineral is very soft (H = 1.5 - 2) 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, in1815 , atTelemarken inNorway ; crystals are fromSchubkau . It often occurs inquartz associated with nativegold .External links
* [http://webmineral.com/data/Tetradymite.shtml Webmineral]
* [http://www.mindat.org/min-3921.html Mindat]References
*1911
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