The Rio Grande claims are underlain by Lower to Middle Jurassic Hazelton Group volcanics which are unconformably overlain by Upper Jurassic to Lower Cretaceous Bowser Group sediments. These rocks are intruded by a Cretaceous Bulkley Intrusion, comprised of grano- diorite and quartz-monzonite. This intrusion forms the core of the highest peak of Mount Evelyn. Minor quartz-feldspar porphyry dikes associated with the Bulkley Intrusive crosscut the volcanics and sediments. The Hazelton Group rocks are comprised of a basal inter- mediate volcanic overlain by massive pale green dacite and rhyo- dacite flows. This is followed by 10 metres of bleached and shattered tuff overlain by massive andesite, andesitic flows and tuff. The Bowser Group unconformably overlies the Hazelton rocks. The sedimentary sequence consists of a poorly sorted basal conglom- erate which exhibits rusty weathering due to disseminated pyrite in the matrix.

The Rio Grande mineral occurrence coincides with shear filling and vein-type mineralization in the conglomerate. This is overlain by a monotonous series of upward fining grits, siltstones, and mudstone which are generally black, carbonaceous and rusty weathered. Shears and fractures are filled with quartz-sulphide veins which range between 5 centimetres to 3 metres thick and contain a variable amount of mineralization.

At an elevation of 1400 metres an adit was driven along the contact of the sediments and volcanics. The contact strikes a little south of east and dips 40 degrees north. Rocks at the dump site for the adit consist of siltstones traversed by fine pyrite seams. In an open cut on the contact there was rusty oxidized rock impregnated with arsenopyrite and pyrite. Similar mineralization occurs east- ward along the contact. A piece of the arsenopyrite taken from a crosscut assayed 25.4 grams per tonne gold and 274.3 grams per tonne silver (Property File - Garde, A., 1934).

Mineralization occurs as infillings in shears and zones of brecciation near the granodiorite intrusion at the volcanics. Adits at 1570 and 1675 metres elevation driven along fissures were both barren.

Imperial Metals Corporation optioned the Chauffer property in 1995. A polymetallic massive sulphide showing was trenched and drilled. A 0.52-metre intersection assayed 18.9 grams per tonne gold and 15.77 grams per tonne silver (Assessment Report 24354).