Images
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:
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).
Localities
At the Mangani mine, West Sumatra Province, Indonesia, pearceite occurs on drusy
quartz
(AM 48.655-572).
At Mineral de Pozos, San Luis de la Paz Municipality, Guanajuato, Mexico, pearceite is associated with
chalcopyrite
(AM 48.655-572).
At the Uchucchacua Mine, Uchucchacua area, Oyón District, Oyón Province, Lima, Peru, pearceite is
associated with
chalcopyrite, and sometimes
proustite
(Minrec 42.2.156).
Pearceite from Uchucchacua - Image
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&M 87.4.304-337).
At the Rico district, Dolores county, Colorado, USA, pearceite is associated with
chalcopyrite and
tennantite
(R&M 87.4.304-337).
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&M 87.4.304-337).
At the Tuscarora Mining District, Elko County, Nevada, USA, pearceite is associated with
pyrite
(AM 48.655-572).
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