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Formula: [Ag9AuS4][Ag6As2S7]
Valence: [Ag1+9Au1+S2-4][Ag1+6As3+2S2-7]
Sulpharsenite,
pearceite-polybasite group,
silver- and gold- bearing mineral
Crystal system: Trigonal
Specific gravity: 6.606 calculated
Hardness: 3
Streak: Black
Colour: Dark grey to black, numerous dark red internal reflections
Luminescence: No fluorescence under UV
Environments
Auropearceite is a new mineral, approved in 2024 and to date (February 2026) reported only from the type
locality.
Localities
At the type locality, Šibeničný vrch, Nová Baňa, Žarnovica District, Banská Bystrica Region, Slovakia,
auropolybasite and auropearceite were found as anhedral
grains up to 0.2 mm in size, usually rimmed by acanthite. Both minerals
are associated with acanthite,
argentopolybasite,
argentopearceite,
pyrargyrite, proustite,
stephanite,
selenostephanite,
rozhdestvenskayaite-(Zn),
zvěstovite-(Zn),
zvěstovite-(Fe),
naumannite,
gold-silver alloys,
uytenbogaardtite,
iodargyrite and
bromargyrite.
Auropolybasite and auropearceite formed in the waning stages
of epithermal systems, where reduced, S-rich, low-salinity fluids transported Au, Ag, Sb, and As as
thiocomplexes (complexes where an O has been replaced by S). These fluids were unable to transport Cu, Pb and Zn,
thus explaining the chemical composition of these minerals and the entire mineral assemblage
(AM 111.2.289-302).
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