The Big Mike occurrence is located just above the high tide mark along the east shore of Portland Canal, south of Bulldog Creek, 10.5 kilometres south of Stewart.

The area is mainly underlain by diorite, minor quartz diorite and granodiorite of the Jurassic Bulldog Creek pluton (Coast Plutonic Complex). These rocks have intruded and contain local remnants of Lower Jurassic Hazelton Group (Unuk River Formation) andesite, siltstone and slate. Silicification of Hazelton Group rocks has occurred at most places along the contact with the Coast Plutonic Complex. Locally, occasional andesite and rare quartz monzonite dikes intrude diorite and granodiorite dikes intrude Hazelton Group andesite.

At the Big Mike showing, short discontinuous quartz veins are emplaced along east to southeast striking, moderate to steeply north dipping faults or shears in granodiorite. The veins have sharp contacts with wallrock but local silicification is evident. Epidote veinlets and patchy epidotization occasionally occur in the quartz veins and within andesite and the intrusive rocks. Mineralization in the quartz veins consists of variable amounts of pyrite, chalcopyrite, galena and sphalerite with associated gold and silver values.

Two historic adits, the Main adit and South adit, are developed on a quartz vein and silicified fault, respectively. The Main adit is along an east trending fault or shear dipping 44 to 72 degrees north. The main quartz vein ranges from 26 to 34 centimetres wide and locally splits into subparallel, discontinuous quartz veinlets 1 millimetre wide. Some of the veinlets are randomly oriented and do not parallel the main vein. The main quartz vein locally contains lenticular inclusions of schistose granodiorite wallrock. Chip samples from the quartz vein in the Main adit assayed up to 6.82 grams per tonne gold and 5.48 grams per tonne silver (Alex Ventures Prospectus, 1987). The South adit, 260 metres southwest of the Main adit, is developed in a highly silicified shear zone striking 166 degrees and dipping 67 degrees east. Two unmineralized quartz veinlets up to 3 millimetres wide and 25 centimetres long were intersected.

Up to 1400 metres south of the South adit, Hazelton Group andesite is locally highly fractured and silicified. Alteration mineralogy consists of quartz, epidote, carbonate, chlorite and limonite occurring as veinlets, pods and patches. Pyrite and pyrrhotite fill fractures and are locally disseminated.