The Jumbo occurrence(s) are located along the southwestern side of Nevada Mountain, north of Lost Creek and between Proctor and Shandley creeks, with a number of adits being developed between elevations of approximately 1500 to 1740 metres.
Regionally, the area is underlain by fine clastic sediments of the Lower to Middle Ordovician Active Formation, sediments and carbonate rocks of the Middle Cambrian Nelway Formation, undivided sedimentary rocks of the Cambrian Laib Formation and quartz arenite sedimentary rocks of the Neoproterozoic to Lower Cambrian Hamill Group, which have been intruded by granodioritic rocks of the Cretaceous Anstey pluton. A small stock of syenitic to monzonitic intrusive rocks of the Eocene Coryell Plutonic Suite outcrops to the west.
Locally, argillites, limy argillites, and grey limestone units, 3 to 10 metres thick, of the Lower to Middle Ordovician Active Formation are in close contact with the western margin of the Lost Creek granite stock of the Cretaceous Anstey pluton. The limestones are locally altered to skarn and carry disseminated scheelite, which has a yellowish fluorescence. A quartz vein follows the granite-skarn contact and is observed to host pyrite with minor galena, sphalerite, and molybdenite.
In 1959, a channel sample across 1.5 metres assayed 0.5 per cent tungsten trioxide and 0.03 per cent molybdenite (Geological Survey of Canada Economic Geology Series No. 17, page 103).
In 1979, a sample (480140) taken near one of the lower adits assayed 0.238 per cent lead and 114.0 grams per tonne silver (Assessment Report 7879).
The area has been explored since the late 1800s or early 1900s, with at least 10 adits or tunnels being developed early in the 19th century. During 1979 through 1981, BP Minerals completed programs of rock, silt and soil sampling; geological mapping and 53.0 line-kilometres of ground geophysical surveys on the M.U.T. claims. During 1994 through 1996, Sultan Minerals Inc. conducted programs of geochemical sampling, geological mapping and a 510 line-kilometre airborne geophysical survey on the area.