The Mollie Mac deposit is at 1400 metres elevation on the steep northwestern slope of Gainer Creek, approximately 4.0 kilometres upstream from Ten-Mile on Lardeau Creek. It is covered by a belt of four crown-granted mineral claims (Milner Fr. (L.14015), Molly Mac 1 (L.10653), Molly Mac 2 (L.11421) and Molly Mac 3 (L.14014)) that straddle Gainer Creek, across from its junction with Index Creek and extend uphill to the northwest. The tenure belt continues to the southeast on the White Quail [082KNW037], Hidden Treasure [082KNW106] and Index [082KNW038] properties.
The Mollie Mac showings were located before 1895 and a short adit was driven at 1356 metres elevation prior to 1925; however, only a minor amount of work was done on the showings before 1951. In that year and the following, Mollie Mac Mines Limited built a road from Ten-Mile and diamond drilled about 610 metres in short holes. It later drove a second adit, 87 metres long, at 1390 metres elevation. Since 1951, most of the company's work has been designed to test the extent of mineralization in the "lower zone", which is below the base of the limestone bluff. The "upper zone" is higher up section in the limestone. There is a caved shaft on the north brow of the ridge about 60 metres to the northwest, beyond the upper showings, and a short adit driven farther to the northwest, over the rise lower down the slope toward Bunker Hill Creek.
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 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 Mollie Mac past producer is in the Molly Mac limestone, a 10 to 30 metres wide unit near the top of the Index Formation. The limestone is thinly banded and underlain by several metres of green and, below that, grey phyllite. It is fine-grained and, towards the top, recrystallized to marble. The surrounding rocks are intensely folded. They strike to the northwest and, for the most part, dip steeply to the southwest. Small dragfolds in and along the contact of the limestone are "N" shaped and plunge at between 5 and 10 degrees to the northwest. The principal zones of mineralization are controlled by tight folds and by faults. The sulphides occur in irregular lenses and zones of siderite replacement after limestone. The lenses are pipe-like and appear to plunge with the axes of the folds. The style of mineralization is similar to that observed on the nearby Index [082KNW038] property.
Galena is the principal ore mineral, though minor amounts of sphalerite, chalcopyrite and pyrite occur. Most of the galena is found with siderite, in massive fine-grained lenses or less commonly as poorly defined disseminations. Locally, galena occurs in limestone as small veinlets or replacements along beds, folds, or fractures. The largest pods of galena probably plunge gently to the northwest parallel to the axes of dragfolds. Other masses of galena are found along discontinuous shear zones within masses of siderite or near their margins. The lenses of galena are a few metres wide and extend a few tens of metres up the slope. Mostly, they are well defined, and siderite altered limestone some distance from a galena-bearing lense is commonly barren. A 76-centimetre sample assayed 61.7 grams per tonne silver and 10.89 per cent lead (EMPR BULL 45).