The mineral petzite, Ag 2, is a soft, steel-gray telluride mineral generally deposited by hydrothermal activity. It forms isometric crystals, and is usually associated with rare tellurium, mercury.
The name comes from chemist W. Petz, who first analyzed the mineral from the type locality in Săcărâmb, Transylvania in 1845. It was described by Wilhelm Karl Ritter von Haidinger in 1845 and dedicated to W. Petz who had carried out the first analyses.
It occurs with other tellurides in vein gold deposits. It is commonly associated with native gold, hessite , sylvanite, altaite, frohbergite, vulcanite
Petzite forms together with uytenbogaardtite (Ag3AuS2) and fischesserite (Ag3AuSe2) the uytenbogaardtite group.