Tags: Chemical Substance, Mineral.
Tetradymite is a mineral consisting of bismuth tellurium and sulfide Bi2Te2S also known as telluric bismuth. If sulfur is absent the mineral is tellurobismuthite and the formula is then Bi2Te3. Traces of selenium 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.
