The Marathon showing is situated on the south side of the Similkameen River, opposite a bend in the river, 14.5 kilometres northwest of Hedley. This region south of the Similkameen River is underlain by granodiorite to quartz monzonite of the Early Jurassic Bromley batholith.

The showing is hosted in a quartz orthoclase porphyritic rhyolite dyke, 5 metres wide, which strikes roughly north and dips steeply west. A zone of shearing, containing sericite, calcite and epidote, occurs in the east wall of the dyke. The zone is 0.6 to 1.5 metres wide and has been traced sporadically in surface and underground workings over a strike length of approximately 500 metres.

The zone is mineralized with rare and erratically distributed stringers and grains of sulphides, including pyrite, chalcopyrite, galena and an unknown fine-grained silvery sulphide (arsenopyrite?). The mineralization is accompanied by some granular quartz and a little manganese staining. Three samples taken from an opencut contained traces of gold and silver (Property File - M.S. Hedley, 1936).

A number of vertically dipping stringers, up to 10 centimetres wide, cut granodiorite, about 0.4 kilometre to the west. The stringers strike 155 degrees and consist of hematite, quartz and minor chalcopyrite. The granodiorite also contains bands and masses of epidote up to 0.6 metre across, some 200 metres farther west. The bands trend 155 degrees and contain small amounts of hematite and traces of chalcopyrite and quartz.

The various showings were explored by an adit 4.6 metres long, and several opencuts and areas of stripping between 1934 and 1936.