The Snowfall occurrence is underlain by Mesozoic quartz diorite and diorite of the Coast Plutonic Complex which intrudes Upper Triassic Karmutsen Formation (Vancouver Group) basalt flows containing some interbeds of limestone. Skarn, consisting of coarse dark brown garnet, epidote, quartz and tremolite, occurs in and near the limestone interbeds. The skarn hosts small stringers and blebs of magnetite with minor amounts of pyrite and rare chalcopyrite. The quartz diorite also contains finely disseminated pyrite and chalcopyrite.