The Coal Creek showing is underlain by Upper Triassic Vancouver Group, Karmutsen Formation basalt, which is unconformably overlain by conglomerates and sandstones of the Upper Cretaceous Comox Formation, Nanaimo Group.

Basalt containing chalcopyrite, native copper, bornite, pyrite and malachite occurs in the area where the Trent River is joined by Tremain and Idle creeks (Assessment Report 17972). Iron carbonate and calcite veining with associated breccia zones are also reported in the area. A small showing of cinnabar was observed in a flat lying calcite vein.