The first occurrence of cupropearceite in the Kupferschiefer deposit, Lubin mine, SW Poland

Cupropearceite is a sulphosalt belonging to the pearceite-polybasite group, formed due to Cu-for-Ag substitution. It is a rare mineral of the Earth’s crust, described only in four locations so far. This work reports the occurrence of cupropearceite in the upper part of the Weissliegend sandstone from the Cu-Ag deposit in the Fore-Sudetic Monocline. The mineral is associated with stromeyerite, bornite, chalcocite, native silver, silver amalgams and, rarely, pyrite. Formation of cupropearceite is related to fluid activity during low-temperature hydrothermal events responsible for the formation of the Cu-Ag ore mineralization. The identification of cupropearceite is important in terms of constraining minerals bearing associated metals, particularly Ag and As. This work also presents occurrence of this rare mineral in the previously unnoted mineral assemblage mentioned above. The presence of cupropearceite confirms a low-temperature, hydrothermal origin of the Cu-Ag deposit in the Fore-Sudetic Monocline.