The Copper Farm prospect is situated on the south side of the Similkameen valley, 500 metres east of Basely Creek and 8 kilometres east of Princeton. This area, on the north flank of the Darcy Mountains, is primarily underlain by intrusive rocks of the Early Jurassic Bromley batholith, with minor volcanics and sediments of the Upper Triassic Nicola Group.
In the vicinity of the deposit, Nicola Group andesites and basalts are intruded by irregular bodies and dykes of granodiorite, granite and quartz diorite related to the Bromley batholith.
A shear zone has been traced southward into the steep south bank of the Similkameen River by two adits (Nos. 2 and 3 tunnels) over a strike length of 200 metres and a vertical distance of 85 metres. The zone strikes almost due north, dips slightly to the west, and varies from a few centimetres to 3 metres in width. It is cut by a barren, pink, quartz porphyry dyke, 18 to 21 metres wide on surface, striking 045 degrees with a dip of about 45 degrees southwest.
Sulphide mineralization is erratic, consisting of disseminations, blebs, lenses and stringers of chalcopyrite, pyrite, tetrahedrite and bornite in a gangue of quartz, calcite, siderite, chlorite and sheared country rock. The sulphides are commonly accompanied by malachite and azurite. Individual sulphide lenses are up to 51 centimetres wide. High-grade mineralization generally occurs over widths of less than 0.3 metre. Twenty-seven chip samples taken over widths of 0.30 to 2.6 metres, in the Nos. 2 and 3 tunnels, assayed trace to 1.4 grams per tonne gold, trace to 78.9 grams per tonne silver and nil to 10.93 per cent copper (Minister of Mines Annual Report 1928, page 262). Seventeen of the samples contained at least 0.70 per cent copper. One sample in particular (No. 13) assayed 1.4 grams per tonne gold, 17 grams per tonne silver and 1.16 per cent copper over 2.4 metres. Other northerly striking shears, sparsely mineralized with chalcopyrite and pyrite, and less than 0.3 metre wide, occur in the vicinity of the old workings.
Discontinuous exposures of mineralization continue on surface farther south, beyond the Nos. 2 and 3 tunnels. A zone of massive pyrrhotite, pyrite, chalcopyrite and tetrahedrite, 100 metres long, occurs just above the No. 1 tunnel, 210 metres south of the collar of the No. 2 tunnel. Also, a vein of massive tetrahedrite, 3 to 15 centimetres wide, is exposed at the top of the valley side, 670 metres south of the No. 2 tunnel. A sample assayed 2.4 grams per tonne gold, 1850 grams per tonne silver and 12 per cent copper (Minister of Mines Annual Report 1922, page 169).
This prospect was explored as early as 1908. Princeton Mining and Development Company Ltd. completed 550 metres of drifting, crosscutting and raising in the Nos. 2 and 3 tunnels between 1920 and 1927, after initially mining 15 tonnes of ore in 1919. The ore graded 15.2 per cent copper and 64.5 grams per tonne silver (National Mineral Inventory card). The company also excavated several smaller adits and numerous trenches and pits. Various operators conducted geological, magnetometer and soil surveys, and 169 metres of diamond drilling in two holes between 1968 and 1983.