The Copper Mountain porphyry prospect, 2.5 kilometres southwest of Trigger Lake, is mainly within a Late Cretaceous pluton consisting of hornblende-biotite granodiorite of the Coast Plutonic Complex. The area to the north is underlain by Upper Cretaceous volcanics of the informally named Powell Creek Formation.

The main mineralized zone occurs within the granodiorite where it contacts a younger(?) diorite porphyry stock. Mineralization comprises pyrite, chalcopyrite, magnetite, quartz, calcite, and traces of bornite and molybdenite as fracture-fillings in brecciated and fractured granodiorite. Commonly, the granodiorite displays an orbicular structure comprising nodules (to more than 1 metre in size) of massive granodiorite separated by mineralized miarolitic granodiorite. Drilling indicates that mineralization also occurs within propylitic-altered andesite north of the granodiorite, where 2 to 7 per cent pyrite with minor chalcopyrite and traces of sphalerite and galena occur as disseminations, blebs, fracture fillings, and irregular massive seams.

A 10-metre chip sample assayed 0.25 gram per tonne silver and 0.28 per cent copper (Property File - Manning, 1967).