The Mill showing is located about 1.6 kilometres southeast of the Venus millsite, north of Tutshi Lake and about 32 kilometres south of Carcross, Yukon Territory.
Near the bend of Tutshi Lake, rocks of Lower Jurassic Laberge Group are in contact with Sinwa limestone (to the west) that caps the Stuhini succession. This contact has been mapped as a thrust fault by Bultman (1979), mainly due to evidence of deformation at the carbonate contacts. Other evidence argues equally that this is an essentially conformable (or disconformable) succession with relatively minor motion on bedding-parallel faults (Bulletin 105). The section dips consistently to the northeast at about 45 degrees. MapPlace shows Upper Triassic to Lower Jurassic conglomeratic strata, atop the Sinwa limestone, to the east, with Inklin Formation (Laberge Group) argillites and wackes atop this conglomerate, to the east. The Sinwa Formation (Suhini Group) is a massive to rarely fossiliferous bioherm/reefal limestone capping conglomerate and coarse clastic sedimentary rock of the Upper Triassic Stuhini Formation succession. The Sinwa limestone can be brecciated, locally argillaceous and fetid. The strata are intruded by Late Cretaceous Coast Plutonic Complex dikes and intrusions.
At the turn of the century, ridges in the area were prospected for Venus vein-type occurrences, and seven pits in the millsite area may date from this period. At the Venus millsite, an adit was driven into altered conglomerate and limestone during the 1970s. The pits were, with one exception, blasted in conglomerate or fine-grained felsic intrusive rock containing copper-lead-zinc mineralization. The one pit was in limestone and contained copper mineralization.
Showings on the Mill claim were discovered during geological mapping and prospecting in 1987 by United Keno Hill Mines. This includes a copper showing, which was found to be hosted in altered conglomerates adjacent to a carbonate ridge.
In 1988, United Keno conducted geophysical surveys and drilling. Drilling in the tailings pond area indicated that skarn alteration of conglomerate units increases with depth. Clast replacement with pyrite, pyrrhotite and chalcopyrite along with epidote, chlorite and carbonate minerals increases with depth. Porphyry dikes were intersected which were not previously mapped on surface. The dikes were strongly altered to clays and contained varying amounts of arsenopyrite-filled fractures and stockworks.
In 1989, mapping, prospecting, and sampling were done on the Mill 1 claim and 2 drillholes were completed on the newly staked Mill 2 claim. This mapping delineated the existence of the altered conglomerate unit along strike towards Tutshi Lake.
The rocks intersected below the carbonate unit, in hole 89-1, were strongly altered and mineralized at the contact but decreased away from the contact. The alteration consists of abundant epidote and chlorite. The host rocks have undergone severe structural deformation as evidenced by breccia zones and abundant quartz veining. As the alteration decreases, the fracturing diminishes, and fracture filling becomes calcite with pyrite as opposed to quartz with chalcopyrite. Most of the mineralization present occurs as sulphide replacement of clasts and matrix. Chalcopyrite, pyrite and pyrrhotite occur in varying amounts up to 30 per cent or more in a 1.4-metre section. This intersection averages 1.58 per cent copper, 41.14 grams per tonne silver and 2.06 grams per tonne gold (Assessment Report 20032). A 4.4-metre intersection averages 0.855 per cent copper, 24 grams per tonne silver and 1.03 grams per tonne gold (Assessment Report 20032).
In 2006, Xplorer Minerals Inc. conducted a regional reconnaissance sampling program on the Chilkoot property which covers the Mill showing (pers. comm., E. Bergvinson, 2008). A rock sample taken from the showing area yielded 1.18 per cent zinc, 9.3 grams per tonne silver, 0.16 grams per tonne gold, 0.14 per cent copper and 0.22 per cent lead (pers. comm., E. Bergvinson, 2008).
