Parasterryite
Parasterryite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Ag₄Pb₂₀(Sb,As)₂₄S₅₈.
It crystallizes in the monoclinic crystal system (space group P2_1/c). It is a member of the Madocite structural group.
Key properties: Mohs hardness 3–4; specific gravity 5.747; Black streak; Metallic luster.
IMA symbol Psty, IMA status: approved, named in 2010.
Found in vugs within hydrothermal barite–quartz veins embedded in barite-pyrite lenses in complexly sheared and metamorphosed sedimentary rocks.
It is found associated with Acanthite, famatinite, geocronite-jordanite, pyrargyrite-prustite, Sb-rich rathite, sphalerite (overgrowth on sterryite), tetrahedrite, xanthoconite.
The name refers to the similarity to sterryite with the Greek prefix para with the meaning “near”.