The Motherlode showings were staked in 1937 on a small south-flowing tributary, about 1.5 kilometres north of its junction with Monk Creek on the southwest slopes of Mount Irene at 1700 to 1850 metres elevation. The Copper Queen (082FSE053) of similar mineralization may adjoin on the south, at slightly lower elevation; see also the Irene (082FSE134) located in Char Creek to the north (Assessment Report 22054).
Mineralization occurs in sheared greenstone of the Irene Volcanic Formation, underlain to the east by pebble conglomerate of the Toby Formation. Both these units are part of the Horsethief Creek Group of Upper Proterozoic age, and are metamorphosed to chlorite facies of regional greenschist metamorphism. Mineralization is associated with a zone of fracturing and veining that trends northerly and dips steeply west, across a maximum width of 6 metres and strike length of 75 metres as exposed in numerous surface trenches and opencuts. In addition to rusty gossan, pyrite, chalcopyrite, pyrrhotite and a little galena are exposed in a gangue of quartz, ankeritic carbonate and sericitic material. Samples of dump material assay up to 2.4 per cent copper, 154 grams per tonne silver and trace gold; rusty gossan (in which gold is probably enriched) assay up to 7 grams per tonne gold (Minister of Mines Annual Report 1937).