The Cultus Creek showing lies at the north end of a band of showings extending from the Humdinger & Hunkadora (082FSE082) and Peanut (082FSE081) locations. The mineralization is variously described as a vein in a mineralized band of altered and silicified limestone contained in a formation of highly metamorphosed sedimentary rocks, or (more recently) as disseminated sulphides in a silicified dolostone unit or units contained in andesitic tuffs.
These rocks, formerly assigned to the Dutch Creek Formation of the Purcell Supergroup of Middle Proterozoic age, have recently been remapped to lie within the Irene Volcanic Formation of the Horsethief Creek Group (Upper Proterozoic Windermere Supergroup). In detail (Assessment Report 10484) they consist of schistose greenstone (possible andesitic tuffs) overlain or intercalated with orange-weathering dolostone, siltstone and phyllitic shales. The granitic Nelson batholith lies to the west of the claims; metamorphic grade is staurolite amphibolite just to the south of the property, but may be greenschist in the area of mineralization.
Lamprophyre dikes are found near but not necessarily associated with the mineralization, which consists mainly of oxidized material containing disseminated pyrite, chalcopyrite and tetrahedrite. At the north end of the mineralized zone (which may be stratigraphically close to that of the Iva Fern showings (082FSE037), 2 kilometres to the northwest), quartz veins in siltstone between two carbonate units assayed up to 0.84 per cent copper, 16 grams per tonne silver and 0.1 gram per tonne gold (Minister of Mines Annual Report 1926).