The Poison Mountain porphyry copper deposit is on the southwest flank of Poison Mountain, 37 kilometres west of the Big Bar cable ferry on the Fraser River.

Mineralization at Poison Mountain is associated with two granodiorite to quartz diorite stocks (the Main and North porphyries) which intrude arkosic sandstones, conglomeratic sandstones and shales of the Lower Cretaceous Jackass Mountain Group. The stocks comprise relatively unaltered cores of hornblende-plagioclase porphyry which grade outwards into biotite-plagioclase porphyry in which the biotite is an alteration product of hornblende. The intrusion, potassic alteration and mineralization at Poison Mountain are about 59 to 56 Ma in age (Paleocene) as indicated by potassium-argon dating of hornblende and biotites from the mineralized system (Canadian Institute of Mining and Metallurgy Special Volume 15).

The highest grade mineralization occurs within the biotite-altered border phases of the intrusions and adjacent biotite- hornfelsed sedimentary rocks. It consists mainly of pyrite, chalcopyrite, molybdenite and bornite, which occur as disseminations and fracture-fillings, and in veins associated with quartz. Calcite and gypsum also occur as hydrothermal minerals, and pyrite, together with magnetite and hematite, forms an irregular halo around the mineralized zone. Chlorite-epidote alteration occurs sporadically within Jackass Mountain Group rocks for several kilometres around the deposit.

Since its discovery in 1956, the property has been explored by a variety of surveys, 17,269 metres of diamond drilling and 21,131 metres of percussion drilling, which has identified two zones. The Copper Creek zone has reserves of 280 million tonnes grading 0.261 per cent copper, 0.142 gram per tonne gold, 0.007 per cent molybdenum and 0.514 grams per tonne silver. The Fenton Creek zone is estimated at 18.3 million tonnes grading 0.31 per cent copper and 0.128 grams per tonne gold (George Cross News Letter No. 65 (April 2), 1993 and Imperial Metals Corporation, 1995 Annual Report).

In 1993, Bethlehem Resources Corporation drilled 10 holes totalling 2569 metres. Imperial Metals Corporation held an option on the property in 1995. In 1994 Barrick Gold Inc. acquired Lac Minerals Ltd. and in 2009 drilled 10 holes, totaling 4894 metres.