Plagionite Locality: San José Mine, Oruro City, Cercado Province , Oruro Department , Bolivia ( Locality at mindat.org ) Size: 3.3 x 3.0 x 1.7 cm. Plagionite is a rare lead-antimony-sulfide. This incredibly rich specimen is relatively large and of high quality for this famous old find....probably dating back over 50 years to the Mark Bandy era in Bolivia. It features sharp metallic crystals to 9mm in size, in an interconnected cluster. For crystal size, and robustness, and overall richness of the piece, this is one of the better surviving examples, I think we could say. Ex. Lawrence Conklin Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Plagionite
Plagionite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Pb₅Sb₈S₁₇.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: Mohs hardness 2.5; specific gravity 5.54; Blackish lead-gray, deep red-brown streak; Metallic luster.
IMA symbol Pgi, grandfathered status — known before the IMA’s founding, named in 1833.
Found in hydrothermal vein deposits.
It is found associated with Cassiterite, franckeite, andorite, semseyite, zinkenite, twinnite, robinsonite, geocronite, boulangerite, galena, pyrite.
Its name comes from the Greek for oblique, in reference to the crystal morphology.