McDonald Island is underlain by Lower Jurassic Hazelton volcanics of the Telkwa Formation comprised of green to purple waterlain andesite tuffs and breccias. These strike northerly and dip at moderate angles to the west and are overlain in the western part of the island by massive and amygdaloidal andesitic flows and thin bedded shales.

Copper mineralization (Granisle Mine 093L 146) is associated with an Eocene Babine Intrusive quartz diorite plug and a biotite-feldspar porphyry dike which strikes northeasterly across the island.

At lake level on the southwest end of the island, 1.2 kilometres south of the pit, a quartz-carbonate breccia vein hosts sphalerite, galena, pyrite, and chalcopyrite. The vein contains some silver and follows a northeast striking fault for a limited distance. The vein strikes 030 degrees and dips approximately 60 degrees southeast. A grab sample is reported to have assayed 3.4 grams per tonne gold, 411.4 grams per tonne silver, 13 per cent lead, and 19 per cent zinc (National Mineral Inventory Card 93L16 Pb1).

HISTORY

The Robin Hood group of claims was staked on the showing bg Nr. C. Newman prior t o 1913 and an adit a t lake level was drive 11 metres. In 1940 the property was owned by E.F. Campbell and associates, of Vancouver, under the name Newman group, comprising the Newman, Home, Jim, Jean, and Nord claims. During the year a shaft was sunk 11 metres from which point the vein was intersected by cross-cutting and explored by lateral drifting. It was reported in 1940 that reported a 60 foot adit had been driven along the hanging wall of the vein.

The Granby Mining Company Limited acquired the showing in 1955 as part of the Granisle property.