The Sentinel occurrence is underlain by massive recrystallized limestone of the Upper Triassic Quatsino Formation near the contact with underlying Karmutsen Formation amygdaloidal basalt, both of the Vancouver Group. The limestone is strongly fractured in a northerly direction and is locally brecciated. Narrow branching calcite vein- lets and irregular patches of calcite are numerous. Occasional dio- rite dykes crosscut the limestone.

Mineralization consists of grains, small clots and veinlets of pyrite, tetrahedrite, galena, sphalerite and chalcopyrite associated with small calcite veins, and occurs in a fractured and somewhat silicified zone within the limestone. A grab sample from a shaft assayed 3.3 per cent zinc, 362.33 grams per tonne silver, 0.77 per cent lead, 0.15 per cent copper and 2.09 grams per tonne gold (Press Release - Vananda Gold Ltd. February 15, 1988).

Past work included pits, open cuts and a shallow shaft. A shipment of 3.6 tonnes of sorted ore was made in 1927 (Minister of Mines Annual Report 1927, page C359).