The Arp, Tanguy and Breton claims cover almost entirely the Lower Jurassic volcanic epiclastics of the Unuk River Formation, Hazelton assemblage. The rocks consist of green, red and purple massive volcanic conglomerate sandstone and breccia with minor intercalated siltstones. Small satellite stocks of Middle Jurassic Texas Creek granodiorite intrusive complex have been mapped near the centre of the Tanguy-Breton claims and to the north and east of the Arp claim. Premier dykes of granodiorite porphyry trend into the claim group from the Silbak Premier mine area about four kilometres to the northwest. Other rock types on the property are a small section of cataclasites and mylonites in the northwest corner of Breton, and a circular outlier of Middle Jurassic volcanic epiclastics of the Betty Creek Formation, Bowser assemblage, which rest unconformably on the Unuk River rocks along the crest of Bear River Ridge.