The Kirkup showing is mainly underlain by Lower Jurassic Rossland Group (Elise Formation) volcanic breccia, volcanic conglomerate, sandstone and greenstone. Underlying these are siltstone shales, limestone and greywacke of the Pennsylvanian to Permian Mount Roberts Formation. Intruding the strata are granodiorite of the Jurassic Nelson Intrusions (Trail pluton). East of the area, the Rossland Group rocks are intruded by monzonite of the Middle Eocene Coryell Intrusions.

The showings lie within the zone of thermal metamorphism associated with the intrusion of the Trail pluton. Mineralization, within an old shaft on the Gold Star Crown grant, consists of massive bands and/or pods of pyrrhotite, pyrite and minor chalcopyrite in volcanics (Elise Formation) or hornfelsed sediments of the Mount Roberts Formation. Also, an adit was driven westwards into granodiorite for approximately 30.5 metres; material on the dump shows disseminated molybdenite and scheelite.