The island is composed of diorite, granodiorite and quartz diorite of the Jurassic to Cretaceous Coast Plutonic Complex. Shear zones crosscut the island in a southwest direction. Fine minerali- zation in the form of pyrite is found disseminated throughout, but most concentrated in the shear zones. Molybdenite is recorded as being found on the island, but later exploration was unable to locate it (Minister of Mines Annual Report 1968, page 73; Assessment Report 3446).

Showing Number Three is described as a 2.4 metre wide zone of highly sheared and altered quartz monzonite, trending 260 degrees with a 60 degree south dip. The mineralization is finely disseminated chalcopyrite with minor pyrite. Copper staining on slip surfaces is common. Aplite dykes with the same attitude as the mineralized zone are common in the surrounding area. A random sample of this mineral- ization had an assay result of 0.09 per cent copper (Assessment Report 3446).