Cuprite-tenorite-chrysocolla (polished cut slice, 10.4 cm across at its widest) from the Paleocene of Mexico.

This is copper oxide rock from Mexico's Milpillas Copper Mine. It contains reddish cuprite (Cu2O - copper oxide), black tenorite (CuO - copper oxide), and slightly bluish-green chrysocolla ((Cu,Al)2H2Si2O5(OH)4·nH2O - hydrous copper aluminum hydroxy-silicate). The mine targets the Milpillas Orebody, a partially oxidized "porphyry copper" deposit. The nonoxidized portions of the deposit have chalcopyrite and bornite disseminated in breccias and stockwork veins, capped by a supergene-enriched blanket of chalcocite. The cuprite-tenorite-chrysocolla only occurs in the oxidized portions of the chalcocite blanket.

Geologic unit & context & age: Milpillas Orebody, Danian Stage, Early Paleocene (63.1 Ma), hosted mostly in rhyolite and porphyritic quartz monzonite stocks emanating from the Cuitaca-Tinaja Batholith (a Laramide Orogeny intrusive complex dating to 63.9 Ma) + Jurassic and Upper Cretaceous-Paleocene volcanics.