At the Elk Horn showing, galena, sphalerite and pyrite occur in calcite and quartz stringers and veins in a fracture zone, about 3.3 metres across, that cuts intrusive rock of the Custer Gneiss. The Custer Gneiss is derived mainly from lower Mesozoic and possibly Paleozoic and Precambrian rocks, and metamorphosed in the Late Cretaceous or early Tertiary.

Limy sediments have been incorporated into the granite gneiss about the fracture zone, as indicated by small, irregular bands or lenses of lime silicate rock. Epidote, pink garnet and calcite are the reported minerals. A sample taken from a 10-centimetre vein near the hangingwall of the ore zone yielded 160.46 grams per tonne silver, 13.76 per cent lead, 6.72 per cent iron and 20.69 per cent zinc (GSC Summary Report 1923A, page 70).

The contact of the granodioritic Oligocene Chilliwack batholith occurs within a few kilometres to the south of the occurrence.