Tellurobismuthite Dimensions: 50 mm × 30 mm × 25 mm; largest crystal: 15 mm Locality: Kutemajärvi mine, Orivesi, Pirkanmaa, Finland Description: Foliated masses to 15 mm in size. This one does have yellowish tarnish but EDS is same as for silvery white sample. — Photo: Jyrki Autio · Public domain
Tellurobismuthite
Bismuth telluride — a layered trigonal mineral that cleaves into flexible sheets.
Intro adapted from Wikipedia (CC BY-SA).
Tellurobismuthite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Bi₂Te₃.
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Tetradymite structural group.
Key properties: Mohs hardness 1.5–2; specific gravity 7.815; Pale lead-gray streak; Metallic, splendent on fresh cleavages. Anisotropism: Weak. R1 –R2: (400) 62.3–62.9, (420) 62.4–63.4, (440) 62.4–63.8 luster.
IMA symbol Tbi, grandfathered status — known before the IMA’s founding, named in 1863.
Typically formed in hydrothermal gold-quartz veins of low sulfur content.
It is found associated with Gold, bismuth, gold tellurides, tetradymite, altaite, chalcopyrite, pyrrhotite.
The name refers to its composition.