The area of the Three Star occurrence is primarily underlain by the Jurassic Hazelton Group volcanic rocks. A zone of shearing up to approximately 6 metres wide and traceable for about 91 metres occurs in andesite. The zone trends 080 degrees and dips 85 degrees to the south. A quartz gangue in the zone hosts chalcopyrite, pyrite and specularite mineralization in the form of bands 1.6 millimetres to several centimetres wide. Mineralized vugs and disseminated pyrite also occur in the andesite.