The Gyp occurrence is 400 metres northwest of the Nettie L. mine [082KNW100]. The showings are on a spur on the southwest slope of Nettie L. Mountain. They are at 1525 metres elevation, approximately 2.0 kilometres north of Lardeau Creek and 1.0 kilometre east of Ferguson Creek. The Nettie L. mine-site area is covered by a well-defined cluster of crown-granted mineral claims. The principal tenures are the Nettie L. (L.4954), Nettie L. Fraction (L.5689), Ajax (L.4955), Copper Reef (L.4957), Lulu Bell Fraction (L.4958) and Good Luck (L.4956). The main access route into the Nettie L. mine was through workings collared on the Lulu Bell Fraction. However, the "lead" was also accessed by means of an adit on the Gyp Fraction (L.5691). The Gyp workings extend onto the adjacent, May Bee (L.4953) claim.

The Gyp Fraction, Nettie L., May Bee and Ajax claims were located in 1892 by Mr. W.B. Pool, who later formed Great Western Mines Limited to develop them. The early development of the Gyp Fraction is not well known as there is some confusion with the IXL (082KNW009) claim short distance to the northwest. Gunning (GSC MEM 161) refers to the Gyp Fraction as the IXL Fraction. The earliest reference is to the May Bee claim, where some rich specimens of native copper were noted at a depth of between 7.6 and 10 metres in 1896. Samples of galena collected at the same time were found to contain between 1000 and 2000 grams per tonne silver and "$6 to $12 in gold". The May Bee was operated by Double Eagle Mining Company Limited at the turn of the century and there are reports of development work, however it is not clear exactly where. They are probably the Gyp workings, which crossed onto the May Bee tenure. In 1901, Great Western Mines Limited acquired the Gyp, along with the Nettie L.and Ajax, and the following year it acquired the Silver Cup [082KNW027] mine - with the intension of putting both operations under the same management. In 1902, it installed an air compressor and a 60-horse power boiler on the Nettie L. property and operated the mine until the higher-grade ores ran out, in 1903. The company then built a 90 tonne/day mill and concentrator, at Five-mile on the Lardeau Creek and constructed a tramway to the Nettie L. The mill was designed to treat lower-grade ore from both the Nettie L. and Silver Cup operations. It was unsuccessful and the Nettie L. mine shut down in 1904.

The Gyp, Nettie L., Ajax and Silver Cup properties were acquired by Ferguson Mines Limited in 1909. The company reopened some of the old workings and completed some development work. The operation was later leased out and a few small shipments were made from the Ajax mine between 1912 and 1914. The IXL Fraction (if the same as the Gyp Fraction), was owned by W. White and G. McLaren in 1929. On it, there was an adit driven for 122 metres. The best mineralization was found in a stope, about 10.7 metres long, 1.22 metres wide and 6.1 metres high, near the face of the adit (GSC MEM 161). There was also a limited amount of work done on the main property in the 1930s and 1940s. After a considerable interval, Trout Lake Mining Company was formed to develop the Gyp [082KNW010], Nettie L. [082KNW100] and Ajax [082KNW099] deposits in 1950. The company rehabilitated the portals and, over the next couple of years, added additional development and conducted a major drill program in the Nettie L and Gyp part of the mine complex. It also enlarged some of the workings, including an old adit on the Gyp fraction.

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 Gyp, Nettie L. Ajax and other tenures on Nettie L. Mountain cover a northwest trending "ledge", approximately 18 metres wide, that contains quartz-carbonate veins that carry pyrite, galena, sphalerite and chalcopyrite, and values in gold and silver. The surface trace is commonly marked by an oxidized "iron cap" that is readily visible in areas of thin cover. The area is underlain by 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 main area of mineralization, encompassing the Gyp, Nettie L. and Ajax mine property, 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. This is a regionally important isoclinal fold that is over-turned to the southwest and plunges at 25 degrees to the northwest. It imparts an axial plane cleavage that strikes to the northwest and dips at 60 degrees to the northeast. The rocks are cut by axial plane shears and northeast trending cross faults. One of the latter displaces the anticline between the Nettie L. and Ajax workings. The ore lenses are controlled by faults and drag folds in the core of the fold structure. In the Nettie L. [082KNW100] mine, they are also found in cross faults. The structure is complicated by locally large displacements on post-mineral faults in the plane of the "main lead".

The main Gyp adit extends for 143 metres southeast along a shear-hosted vein on the northeast contact of the Ajax quartzite. At it's portal, and for a distance of 30 metres in, the vein is 1.0 to 1.22 metres wide and has a narrow streak of galena and sphalerite along its footwall side. The vein occasionally swells to form ore lenses. As described by Gunning (GSC MEM 161) the IXL fraction adit was driven for 122 metres on a shear zone in dark grey quartzites, interbedded slates and graphitic schists. The shear zone contains a quartz-carbonate vein that is up to 1.52 metres wide and contains small amounts of pyrite, sphalerite, galena, chalcopyrite and tetrahedrite in bunches and streaks. The largest shoot was in a stope about 10.7 metres long, 1.22 metres wide and 6.1 metres high near the face of the adit. Trout Lake Mines Limited drove a new adit at a lower elevation and encountered a small lens of galena-bearing quartz along the quartzite-schist contact. The company diamond drilled the Gyp zone from the adit in the early 1950s and produced approximately 610 meters of core.

A sample of fine-grained ore from Gyp Fraction assayed 3.77 grams per tonne gold, 476.6 grams per tonne silver, 16.5 per cent lead and 33.4 per cent zinc over 0.15 metre (EMPR AR 1925).