Metallic sharp crystals of the very rare mineral hedleyite (a bismuth telluride) from the type locality in Hedley (Good Hope Mine, Hedley, Osoyoos District, British Columbia, Canada) on a quartz matrix. — Photo: David Hospital · CC BY-SA 4.0
Hedleyite
Hedleyite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Bi₇Te₃.
It crystallizes in the hexagonal crystal system. It is a member of the Tetradymite structural group.
Key properties: Mohs hardness 2; specific gravity 8.81–8.91; Metallic. Anisotropism: Slight, pale gray to dark gray. R1 –R2: (400) 59.0–61.8, (420) 59.3–62.5, (440) 59.9–63.3 luster.
IMA symbol Hdl, grandfathered status — known before the IMA’s founding, named in 1945.
Typically a late-stage hydrothermal mineral in quartz veins and massive sulfides in association with skarns and breccias; less commonly in pegmatites.
It is found associated with Bismuth, bismuthinite, tellurobismuthite, tsumoite, joséite, hessite, maldonite, gold, arsenopyrite, pyrrhotite, chalcopyrite, galena, sphalerite, pyrite.
The name is derived from the locality being near Hedley, Canada.