Carrollite, CuCo2S4, is a sulfide of copper and cobalt, often with substantial substitution of nickel for the metal ions, and a member of the linnaeite group.

[11] The one missing electron per four sulfur atoms is delocalized, leading to metallic conductivity and even superconductivity at very low temperatures, combined with a complicated magnetic behavior.

Carrollite occurs in hydrothermal vein deposits[14] associated with tetrahedrite, chalcopyrite, bornite, digenite, djurleite, chalcocite, pyrrhotite, pyrite, sphalerite, millerite, gersdorffite, ullmannite, cobaltoan calcite, and with linnaeite group members linnaeite, siegenite and polydymite.

With decreasing temperature, at 880 °C a carrollite-linnaeite solid solution develops, becoming more copper-rich on cooling, with the carrollite composition at about 500 °C.

[15] Carrollite is found worldwide; reported in Australia, Austria, Azerbaijan, Brazil, Bulgaria, Canada, Chile, China, the Czech Republic, the Democratic Republic of Congo,[16] France, Germany, Japan, Morocco, Namibia, North Korea, Norway, Oman, Poland, Romania, Russia, Slovakia, Sweden, Switzerland, US and Zambia.