The Iron Mountain showing is located near the eastern margin of the Stikinia Terrane 31 kilometres south of Quesnel in south central British Columbia. The dominant rock types in the region are meta- basalt, limestone and argillaceous metasediments of the Mississippian to Triassic Cache Creek Group. These are intruded by the dioritic to quartz dioritic Granite Mountain Pluton and the (?)Cretaceous Sheri- dan Creek Pluton. Jurassic sedimentary rocks overlap both the Cache Creek and Quesnellia terranes to the north and east of the plutons. Older rocks are largely obscured by plateau basalt of probable Miocene age to the west.

The Granite Mountain Pluton has been affected by regional metamorphism (greenschist facies) and deformation along with the enclosing Cache Creek Group. The Cache Creek Group and the margins of the Granite Mountain Pluton record effects of ductile deformation. The main body of the pluton has been cataclastically deformed.

The Iron Mountain showing is underlain by thin bedded metamorphosed basaltic tuffs and related rocks ("greenschist") , volcanic breccia and marble of the Cache Creek Group and, in the north, granite. Mineralization consists of magnetite, specular hematite and chalcopyrite with garnet, pyroxene and epidote as contact metasomatic lensoid deposits within marble and schist. The lenses range in size from a few centimetres in width up 1.2 metres and up to 60 metres long and have been traced over a distance of over 1.5 kilometres. The lenses are conformable with the foliation of the enclosing rocks. Chalcopyrite and pyrite occur disseminated through- out the schists and along shears in the intrusive rocks. Pyrite, chalcopyrite and molybdenite are also present in quartz veins.