Cuprite, Flambeau Mine, Rusk County, WI. Octahedral crystal on gossan. Crystal is about 0.05 mm. long. (Photo and specimen by Dan Behnke)

Formula: Cu2O Isometric


Brilliant red cuprite crystals
Cuprite, Flambeau Mine, Rusk County, WI. Fibrous chalcotrichite. Vertical field of view is about 0.3 mm. (Photo and specimen by Dan Behnke)

Cuprite generally forms from the alteration of preexisting copper minerals during weathering or interaction with groundwater in the supergene and oxidized zones over copper deposits.

DOUGLAS COUNTY: Cuprite is found with native copper and malachite at the Weyerhauser Mine, NW SE Sec. 12 T.42N R.10W (Grant, 1901).

GRANT COUNTY: Cuprite is reported associated with chalcopyrite and malachite from near Boscobel (Hobbs, 1905)

IOWA COUNTY: Found as dark red masses and long acicular red crystals (chalcotrichite) at the Eberle Mine, 5 miles north of Cobb (NW NW Sec. 2 T.6N R.1E). Here it is associated with chalcopyrite, tenorite, malachite, azurite, aurichalcite, sphalerite and smithsonite (Heyl et al., 1959).

LAFAYETTE COUNTY: Cuprite is formed by the weathering of chalcopyrite at a small copper prospect south of Ames Branch, NE SE Sec.22 T.2N R.3E in the Calamine quadrangle (Klemic and West, 1964).
— Cuprite occurs at an old copper prospect about 4 miles NW of Gratiot, SE NW Sec. 36 T.2N R.3E. Here it is described as “abundant” with other secondary minerals such as tenorite, malachite, copper, azurite and chalcocite. The primary copper minerals here are chalcopyrite and bornite (Heyl et al., 1959).

POLK COUNTY: Massive cuprite associated with chalcocite and malachite is found in quartz veins in the north quarry of the Dresser Trap Rock Company property at Dresser at Sec. 5 and 6 T.33N R.18W (Cordua, 1989).

RUSK COUNTY: Massive, octahedral and acicular red crystals (“chalcotrichite”) occur as a minor component of the oxidized zone over the Flambeau ore deposit near Ladysmith (May, 1977, Rosemeyer, 1995, 1996).

WINNEBAGO COUNTY: Cuprite was reported at the old Lutz quarry in the west part of Oshkosh along route 44 in T.18N R.16W. Here it was associated with bornite, covellite, pyrite, marcasite, calcite, galena and sphalerite (USGS, 1976)>