Argentopyrite is a rare silver iron sulfide and a dimorph of sternbergite. It forms monoclinic (pseudohexagonal), bronze-brown, prismatic, metallic, crystals; interpenetration and lamellar twinning are common. It was named in 1868 for its relationship to pyrite and silver content. Argentopyrite forms in hydrothermal veins with proustite and siderite at the type locality: Jachymov (St. Joachimsthal), Jachymov district (St. Joachimsthal), Krusne Hory Mts (Erzgebirge), Karlovy Vary Region, Bohemia (Bohmen; Boehmen), Czech Republic. Other notable localities include: Freiberg, Saxony, East Germany; Broken Hill, New South Wales, Australia.
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