The Cosalite showing lies within the Barkerville Terrane of the Omineca Belt. The Barkerville Terrane is in thrust contact with Triassic Quesnellia Terrane rocks to the west and Hadrynian to Lower Paleozoic Cariboo Terrane rocks to the east. The Barkerville Terrane in this region is underlain by the dominantly metasedimentary rocks of the Hadrynian to Lower Paleozoic Snowshoe Group. In this area the Snowshoe Group comprises limestone, phyllite and quartzite. These rocks have been regionally metamorphosed to greenschist facies.

The showing comprises an area of quartz veining in which veins both cut and are conformable with bedding. The veins, up to 3.5 metres wide, are exposed for up to 4 metres along strike. They contain galena and pyrite mineralization with trace amounts of gold and silver.