The Jumbo prospect is at 1350 metres elevation on Six-Mile Creek, a tributary of Lardeau Creek, east of Ferguson. It is on the Jumbo (L.7052) claim, which was originally part of the "Union Jack Group" of seven claims, which included the Union Jack (L.7049) and, most likely, the Florence (L.7051) claim. The latter is described separately.

By 1899, a crosscut had been driven for 23 metres to intersect a 1.8 metres wide quartz vein at a depth of 21 metres below surface. The tunnel was then continued as a drift. The following year, a new crosscut was stared, either at lower elevation or on the nearby Union Jack tenure. It is not clear from the description. By 1903, this adit had been driven for 31 metres and had cut the vein at a depth of 76 metres. The Union Jack claim or group was reportedly owned by J.C. Kirkpatrick et al. in 1904. There is no mention of old workings in reports written on the Jumbo in the the 1980s and 1990s.

In the early 1980s, Westmin Resources Limited conducted stream and soil geochemical surveys to the north and west of Lardeau Creek and identified several geochemical anomalies on the lower slopes of Nettie L. Mountain. In 1986, Camfrey Resources Limited followed up some of these anomalies and located the "Jumbo" zone on the Jumbo claim, west of Six-Mile Creek. The following year, it trenched the anomaly. At the same time Nortran Resources Limited and Mulitplex Resources Limited, who also had interests in the area, flew an airborne geophysical survey in the area, including the nearby True Fissure [082KNW030] and Nettie L. [082KNW100] deposits, and located a cluster of encouraging electromagnetic responses west of Finkle Creek. In 1993, Contiki Resources Limited acquired the Jumbo showing and also took out an option to acquire 80 percent of Nortran's interest in the area. In 1994, the company conducted more grid work in the Jumbo area. In 1997, Vision Incorporated resampled the area using a soil auger.

The Trout Lake area is underlain by a thick succession of sedimentary and volcanic rocks of the Badshot Formation and Lardeau Group near the northern end of the Kootenay arc, an arcuate, north to northwest trending belt of Paleozoic and Mesozoic strata that is now classified as a distinct, pericratonic, terrane. The arc rocks are bordered by Precambrian quartzite in the east and they young to the west, where they are bounded by Jurassic-age intrusive complexes. They were deformed during the Antler orogeny in Devonian-Mississippian time and were refolded and faulted during the Columbian orogeny, in the Middle Jurassic. A large panel, the "Selkirk allochthon", was later offset to the northeast by dip-slip motion along the Columbia River Fault.

The Badshot Formation is composed of a thick Cambrian limestone that is a distinctive marker horizon in the Trout Lake area. It is underlain by Hamill Group quartzite and it is overlain by a younger assemblage of limestone, calcareous, graphitic and siliceous argillite and siltstone, sandstone, quartzite and conglomerate, and also mafic volcanic flows, tuffs and breccias, all of which belong to the Lardeau Group. The rocks are isoclinally folded and intensely deformed, but only weakly metamorphosed. They occur as intercalated beds of marble, quartzite and grey, green and black phyllite and schist. Fyles and Eastwood (EMPR BULL 45) subdivided the group into six formations (Index, Triune, Ajax, Sharon Creek, Jowett and Broadview) of which the lowermost (Index) and uppermost (Broadview) are the most widespread. The Triune (siliceous argillite), Ajax (quartzite) and Sharon Creek (siliceous argillite) are restricted to the Trout Lake area. The Jowett is a mafic volcanic unit.

The Nettie L, Ajax and Gyp area is underlain siliceous argillites of the Triune and Sharon Creek Formations, by quartzite of the Ajax Formation and by grits and black phyllites of the lower part of the Broadview Formation. The rocks are folded, deformed and locally highly schistose. The area encompassed by the mine is bounded on the northeast by the Cup Creek Fault, on the southwest by the (probably faulted) base of the Broadview Formation and on the southeast by the Brow Fault. The zone is 1000 metres long and 200 to 250 metres wide, and covers a portion of the core of the Silver Cup Anticline, a regionally important isoclinal structure that plunges at 25 degrees to the northwest. The area is also cut by northeast trending cross faults. One displaces the anticline between the Nettie L. and Ajax workings. The ore lenses are controlled by faults and drag folds associated with the anticlinal structure, which is over-turned to the southwest. Its axial plane dips at 60 degrees to the northeast. On the Nettie L. [082KNW100] they are also found on cross faults. There are three relatively large, north-northeast striking structures in the mine area, as well as post-mineral faults that have caused large displacements to occur in the plane of the "main lead". The Nettie L. "ledge", is a northwest trending structure that contains quartz veins with variable amounts of pyrite, galena, sphalerite and chalcopyrite and erratic values in gold and silver. The surface trace is marked by an oxidized "iron cap" that is readily visible. Most of the development work has been on the Nettie L. [082KNW100] and Ajax [082KNW099]. However, the "ledge" crosses the Ajax claim boundary onto the Brow claim, and from there onto the Raven, which is part of the Silver Bell group. From there, it most likely projected onto the Jumbo [082KNW211] and Florence [082KNW013] properties.

The Jumbo prospect is underlain by isoclinally folded and variably schistose siliceous argillite of the Triune Formation, quartzite of the Ajax Formation and siliceous argillite of the overlying Sharon Creek Formation. The rocks strike to the northwest and dip moderately to steeply to the southwest.

Exploration in the late 1890s located a quartz vein on the Jumbo Claim that was 1.8 metres wide and included a small vein of galena that was of particular interest to the owners. The vein also included pyrite "carrying small gold values" and considerable galena sprinkled throughout. The second adit, excavated at the turn of the century, exposed a similar quartz vein. It was 2.4 metres wide and contained "concentrating ore" that assayed 1028 grams per tonne silver and "$10/ton" gold.

The geochemical surveys conducted in the early to mid 1980s produced an irregularly-shaped silver-in-soil anomaly that covered the axis of a complicated fold structure. Its location with respect to the Jumbo vein is unknown. Later work suggested that there were two parts to the geochemical anomaly; however, neither source has been identified.