The Joker prospect is in the upper drainage basin of the Kokanee glacier, 25 kilometres east of the town of Slocan, in Kokanee Glacier Provincial Park. Access to the property is 32 kilometres by road from Kaslo, on Kootenay Lake, up Kaslo and Keen creeks and thence 2.5 kilometres by trail to the Joker Lakes.
Between 1898 and 1900, about a dozen claims were staked adjacent to Joker (Twin) Lakes and a large aggregate amount of work was done at widely separated points. The area was at this time known as Camp Mansfield and operations were conducted by two companies, the Klondike Chimps d'Or Company, a French company for which Earnest Mansfield was manager, and The Excelsior Gold Mining Company Limited Liability, which was formed in 1897. In 1900 the Joker (Lot 3891) and Derby claims were Crown-granted to the Excelsior company; the Treadwell (Lot 4118), Philomene and Tony claims, and the Green Lakes, Marguerite and Alice fractional claims were Crown-granted to Rene Laudi; the Apex, Crescent, Twin Lakes, and Green Lakes claims were Crown-granted to W.E. Boie.
On the east side of the southern lake, on the Tony claim, a crosscut tunnel said to be between 213 and 274 metres long was not driven far enough to reach its objective, a vein outcropping on the mountain slope above. At the 2274-metre elevation on the Joker claim an inclined shaft is said to be 29 metres deep on a 65 degree slope. On the side hill above the shaft a tunnel is said to have been driven westerly about 30 metres on a vein mineralized with pyrite, galena, and sphalerite, but the portal was later obscured by slide rock and vegetation. Open cutting was done on the Treadwell claims on the supposed extension of the shaft vein. On the northern boundary of the Treadwell claim a tunnel was driven for 20 metres along a fracture up to 55 centimetres wide and dipping 65 degrees east in which there is disseminated pyrite as well as some galena, sphalerite, and chalcopyrite; at 16.7 metres in from the portal there is a 3-metre winze. On the northern boundary of the John A claim a tunnel was driven 91.4 metres along a small quartz vein (strikes 055 and dips 85 degrees southeast) following a line of jointing in the granite. The quartz and wall rocks are both stained with secondary copper minerals and carry a little galena and tetrahedrite.
A sample of a vein taken in 1987, assayed 3.8 grams per tonne gold, 42 grams per tonne silver, 0.0057 per cent copper, 0.94 per cent lead, 0.44 per cent zinc (Open File 1988-11).
