The Cas 3-9 occurrence is located at an elevation of approximately 1180 metres on a southeast-trending ridge, approximately 600 metres west of Thutade Lake and 6 kilometres east-southeast of Thomas Peak, about 196 kilometres north-northwest of the community of Germansen Landing.

Regionally, the area is situated within a Mesozoic volcanic arc assemblage, which lies along the eastern margin of the Intermontane Belt, a northwest-trending belt of Paleozoic to Paleogene sediments, volcanics and intrusions bounded to the east by the Omineca Belt and to the west and southwest by the Sustut and Bowser basins. Devonian to Permian Asitka Group crystalline limestones are the oldest rocks exposed in the region. They are commonly in thrust contact with Upper Triassic Stuhini Group andesite flows, pyroclastic rocks and marine sedimentary rocks. The Asitka and Stuhini group rocks have been intruded by the Early Jurassic granodiorite to quartz monzonite Black Lake Suite and are in turn unconformably overlain by or faulted against Lower Jurassic calc-alkaline volcanics of the Toodoggone Formation (Hazelton Group). To the west these units are overlain by sedimentary rocks of the Middle to Upper Cretaceous Sustut Group.

The dominant structures in the area are steeply dipping faults that define a prominent regional northwest structural fabric trending 140 to 170 degrees. High angle, northeast-striking faults (approximately 060 degrees) appear to truncate and displace northwest-striking faults. Collectively these faults form a boundary for variably rotated and tilted blocks underlain by monoclinal strata.

Locally, a lapilli tuff hosts a multi-stage quartz vein with silver values. In 1992, a sample (4697) assayed 106 grams per tonne silver (Assessment Report 22721).

During 1984 through 1988, Pacific Ride Resources Corp. and Hermes Ventures Inc. examined the area as the Lake 4 claim. In 1991 and 1992, Placer Dome Inc. completed programs of rock and soil sampling, geological mapping and ground electromagnetic, magnetic and induced polarization surveys on the area as the Cas 3 and 6-9 claims.