Sulphosalt, paramorph of xanthoconite, above 300oC forms a series with pyrargyrite (AM 48.725-736)
Specific gravity: 5.5 to 5.7
Streak: Scarlet red
Solubility: Slightly soluble in nitric acid
Common impurities: Sb
Proustite is a late-forming mineral in hydrothermal deposits, in the oxidised and enriched zone, associated with other
and sulphides. Associated minerals include silver, arsenic,
acanthite, tetrahedrite and
the type locality is Jáchymov, Karlovy Vary District, Karlovy Vary Region, Czech Republic.
At the Imiter mine, Imiter District, Tinghir Province, Drâa-Tafilalet Region, Morocco, proustite is abundant as small crystals in lead-rich quartz masses; less commonly it is found in black shale, and very rarely in dolomite cavities. Associated minerals include galena, quartz, xanthoconite, polybasite - pearceite, native silver and, less abundantly, imiterite (Minrec 42-2.127-128).
At Tamdrost, Zagora Province, Drâa-Tafilalet Region, Morocco, proustite occurs in calcite veins as crystals to 4 mm with löllingite and native silver (Minrec 38.5.388).
At the Uchucchacua mine, Oyon Province, Lima, Peru, proustite crystals to 1 cm have been found on pearceite crystals (Minrec 42.2.156).
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