Silvery crystal aggregates and crystals of the very rare minerals paracostibite and costibite, from Getön Silver Mine, Persberg, Filipstad, Värmland County, Sweden. Both minerals occur together in the TL. Associated to golden chalcopyrite. Paracostibite-costibite in visible crystals like in the photo is very rare. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Paracostibite
Paracostibite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula CoSbS.
It crystallizes in the orthorhombic crystal system (space group Pbca). It is a member of the Löllingite structural group.
Key properties: specific gravity 6.9; Metallic luster.
IMA symbol Pcsb, IMA status: approved, named in 1969.
Found in drill core from a massive base-metal sulfide deposit in a carbonatized chlorite-anthophyllite schist that is most likely an altered mafic rock, in a sequence of metavolcanics and metasediments (Trout Bay, Canada).
It is found associated with Sphalerite, chalcopyrite, galena, pyrargyrite, pyrrhotite, antimonial silver (Trout Bay, Canada); costibite, nisbite, chalcopyrite, pyrrhotite, galena.
The name refers to CObalt and antimony, STIBium, in the chemical composition and probable structural relation to pararammelsbergite.