The Homestake showings are hosted by the Lower-Middle Jurassic Rossland Group (Elise Formation) augite porphyry. The porphyry is known as the Rossland sill and is dark green with phenocrysts of augite which are partly altered to hornblende. The Rossland Group rocks are intruded by the Early Jurassic Rossland monzonite which consists of a biotite-hornblende-augite monzonite stock. The Homestake veins lie in the zone of thermal metamorphism associated with the monzonite intrusive. The ore in the Homestake vein system, which strikes 100 degrees is classed as transitional-type which is a gradational mineralogy and metal content between the Rossland-type and the South belt-type (Bulletin 74, page 39).

The main mineralized vein on the claim strikes east and dips 70 degrees north and is traceable in excess of 210 metres in length. The ore consists of pyrrhotite, pyrite, sphalerite, galena, marcasite and arsenopyrite in a calcite, quartz and altered country rock gangue. In 1903, the ore assayed an average of 1.37 grams per tonne gold, 96.0 grams per tonne silver, and 0.3 per cent copper (Geological Survey of Canada Memoir 77, page 166).

Another vein strikes 280 degrees and dips steeply to the north and hosts pyrite, pyrrhotite with minor chalcopyrite and magnetite. The vein is 1.8 metres in width and hosts 22.9 centimetres of sulphides on the footwall with 46 centimetres on the hanging wall. The sulphides are part of a magnetite-skarn which occurs in the altered wallrock in a well-defined fracture and/or fault zone. This main fault averages 7.6 centimetres in width. The ore shoots end abruptly against cross structures comprised of lamprophyre and dioritic dykes.

In 3 years, between 1901 and 1908, 236 tonnes of ore were mined and 933 grams gold, 74,927 grams silver, and 91 kilograms copper were recovered.