Copper-nickel mineralization at the mine is associated with semi-massive to disseminated pyrite at the lower contact between altered gabbro and rhyolite of the Temagami Greenstone Belt. The gabbro is steeply dipping, approximately 250 m thick and has a strike extent of at least 5 km. The intensity of mineralization varies greatly but is present over most of the defined strike length of the gabbro. Copper is associated with chalcopyrite. Nickel is associated with millerite, gersdorffite, linnaeite and cobalt-nickel sulfarsenides.
Copperfields Mine is the discovery site of a bright white mineral called temagamite. It was discovered in 1973.