The Nettie L. mine is at 1525 metres elevation on a spur on the southwest slope of Nettie L. Mountain. It is 2.0 kilometres north of Lardeau Creek and 1.0 kilometre east of Ferguson Creek. The mine area is covered by a cluster of crown granted mineral claims that includes 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 principal workings are on the Lulu Bell Fraction and access the main "lead" on the Nettie L. claim. The "lead" was also mined through adits on the Gyp Fraction (L.5691) and the Copper Reef. The latter led to workings on the Ajax claim. In 1929, Gunning (GSC MEM 161) appears to describe the Gyp Fraction as the I.X.L. Fraction and there may be some confusion with the I.X.L. claim, which is further to the northwest.

The Gyp Fraction, Nettie L., May Bee and Ajax claims were located in 1892 by Mr. W.B. Pool, who went on to form Great Western Mines Limited, in 1901, to develop them. The company also acquired the Silver Cup [082KNW027] mine, south of Lardeau Creek, the following year - with the idea 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 ran the mine until the higher-grade ore shoots ran out, in 1903. The company then built a 90 tonne per day mill and concentrator, at Five-mile on the Lardeau Creek and erected a tramway to the Nettie L.. The mill was designed to treat lower-grade ore from the Nettie L. and Silver Cup operations; however, it failed to do so and the Nettie L. mine closed down in 1904.

The Nettie L. and Silver Cup operations were acquired by Ferguson Mines Limited, in 1909, but the Nettie L. remained idle until 1912. That year, Daney and Company completed about 38 metres of sinking and drifting under lease. In 1917, the mine was leased by McLaren, White and Cameron. In 1930, Gold Prospects Limited took an interest in the operation and, in 1936, Security and Investment Corporation Limited made repairs to the road and buildings. A decade later, Cansil Consolidated Mines Limited optioned the property, reopened the adits and again made necessary repairs to the infrastructure. The company then installed a compressor and did some diamond drilling. In 1950, Trout Lake Mining Company was formed to develop the Nettie L. [082KNW100], Ajax [082KNW099] and Gyp [082KNW010] deposits. Once again, the old workings were rehabilitated; however, this time a new adit was driven into the nose of the ridge, at 1556 metres elevation. By then, the Nettie L. had over 2100 metres of workings on four levels over a short, 100 metres difference in elevation. The only work carried out below the lower adit level was conducted in the Daney shaft. In the 1950s, there was considered to be significant potential to depth, under the old workings.

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 (EMPE 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, Gyp 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 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. It 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".

Mineralization at the Nettie L. mine is found in interconnected silicified and carbonatized shears and cross-structures that were accessed at two adit levels, three internal levels and a number of sub-levels. The lower adit is at 1478 metres elevation. It crosscuts to the "main lead" on the No. 4 level and follows it to the southeast. The upper adit is at 1550 metres elevation on the No. 1 level. It crosscuts to the same structure and drifts along it to the northwest and to the southeast. The adit's two levels are connected by raises, and the ore lenses were locally stoped to surface. On surface, the sulphides are oxidized and the veins were found to be covered by an iron-rich cap.

There are two styles of mineralization in the Nettie L. mine. The "main lead" veins are more or less conformable to stratigraphy and structure. They are northwest trending, steeply southwest dipping, fault-controlled, shear-hosted structures. The "big quartz vein", is a quartz stringer system in graphitic schist, slate and quartzite that is related to the "main lead" system but is slightly discordant to it. The "main lead" veins and subsidiary stringers contain quartz, a little ankerite and an abundance of country rock fragments. They are sparingly mineralized with pyrite, sphalerite and galena, except where cut by cross structures. There, they have been stoped. Throughout most of the mine, the principal "main lead" veins consist of a hanging wall zone of gouge and breccia, and a footwall zone of quartz and carbonate separated by a slick, planar fault surface. Most of the ore was in the breccia zone. Veins of barren, massive pyrite, up to 0.3 metre wide, occur both in the breccia and the footwall and other carbonate rich zones. The "cross-lead" veins strike 045 degrees, dip at 70 degrees to the southeast and intersect the "main lead" vein system. In some places the "cross-lead" structures appear to be oriented almost parallel to the "main leads" and merge with them. Most of the ore came from the principal "cross-lead" vein, which was stoped to surface. It was a quartz-carbonate-sulphide vein in a tension fracture. It had sulphide-rich lenses containing sphalerite and galena, and probably also tetrahedrite. The sulphide-rich shoot stopped abruptly on meeting the "main lead" without any sign of faulting, and it died out away from the "main lead" structure.

The ore appears to have been scattered in relatively small, commonly faulted, lenses throughout the mine. Fyles and Eastwood (EMPR BULL 45) provide assays for two of the "better mineralized" exposures. They contain 1.37 and 1.02 grams per tonne gold, 702.8 and 174.9 grams per tonne silver, 0.38 per cent and a trace copper, 1.39 and 1.46 per cent lead and 3.5 and 2.5 per cent zinc, over 0.91 and 1.22 metres respectively. They also show that one of the pyrite veins contains 0.34 grams per tonne gold and 48.0 grams per tonne silver over 0.82 metre. The lowest workings in the mine are at the foot of the Daney shaft where a quartz vein was traced for 6.1 metres. It contained a "small slash" exposing 1.17 metres that was rich in sphalerite.