The area is underlain by Jurassic to Tertiary Coast Plutonic Complex rocks consisting of diorite and tonalite. The intrusive rocks contain minor volcanic and sedimentary roof pendants where the sedimentary pendant rocks are commonly limestone containing numerous dykes. Sulphide mineralization occurs in skarn developed in the limestone near intrusive contacts.

The John Bull occurrence comprises an intensely sheared and brecciated, northwest trending crystalline limestone pendant hosted within tonalite. The pendant is generally 30 to 60 metres wide but locally is 106 metres wide and appears to be caught up in a fault zone which strikes 320 degrees. Banding in the limestone indicates a northerly strike with an 85 degree east dip. The limestone con- tains numerous mafic, felsic and tonalite dykes which are cross- cutting and also conformable to bedding. Many of the dykes are located along shear zones and several terminate against faults.

Irregular, siliceous epidote-garnet skarn is developed in limestone near the intrusive dykes, small diorite plugs and the basement intrusive rocks. Mineralization in the skarn zones is erratic and consists of locally massive and commonly widespread disseminated sphalerite and chalcopyrite with minor amounts of magnetite, pyrite and pyrrhotite. Minor galena and rare molybdenite have also been reported to occur. Massive magnetite is locally developed in epidote-garnet skarn in a surface pit and in a drill core intersection. The best assays from several samples were 52 per cent zinc, 150.83 grams per tonne silver, 0.8 per cent copper, 2.0 per cent lead and 23.99 grams per tonne gold (Minister of Mines Annual Report 1926, page A312).

Past work included several shallow shafts and numerous open cuts.