Pearceite

pearceite

tennantite

polybasite

berzelianite

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Formula: [Ag₉CuS₄][(Ag,Cu)₆(As,Sb)₂S₇]
Sulpharsenite, pearceite-polybasite group, forms a series with polybasite
Crystal System: Trigonal
Specific gravity: 6.15 measured, 6.07 calculated
Hardness: 3
Streak: Reddish black
Colour: Black with dark red internal reflections
Common impurities: Zn,Fe,Sb
Environments:

Hydrothermal environments

Pearceite is an arsenic-bearing mineral that occurs in hydrothermal deposits formed at low to medium temperatures associated with acanthite, silver, proustite, quartz, baryte and calcite (HOM).

At Pozos, Mexico, pearceite is associated with chalcopyrite (AM48.655-572).

At Tuscarora, Nevada, USA, pearceite is associated with pyrite (AM48.655-572).

At the Mangani mine, Sumatra, pearceite occurs on drusy quartz (AM48.655-572).

At Uchucchacua, Lima department, Peru, pearceite is associated with chalcopyrite, and sometimes proustite (Minrec 42.2.156).

At Silver Plume, Cochise county, Arizona, USA, pearceite is associated with galena. Separately, pearceite-polybasite twins are scattered on partially resorbed crystals of acanthite after acanthite variety argentite) (R&M87.4.304-337).

At the Rico district, Dolores county, Colorado, USA, pearceite is associated with chalcopyrite and tennantite (R&M87.4.304-337).

At Smuggler Hill, Lake county, Colorado, USA, pearceite is found as intergrowths with baryte and occasionally with galena or tennantite. Native silver is often found replacing pearceite (R&M87.4.304-337).

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