The Cap showing occurs within the Pacific Ranges within the Coast Crystalline belt near its margin with the Intermontane belt. Rocks of both belts are recognised in the region and comprise andesitic volcanic rocks of the Upper Triassic Cadwallader Group and quartz diorite of the Jurassic to Tertiary Coast Plutonic Complex.

The Cap showing is located near the contact of quartz diorite and Cadwallader Group andesite. The showing comprises disseminated pyrite and chalcopyrite. Although this showing is assumed to be of porphyry type, no confirmation could be made of its nature.