The area is underlain by rock of the Lower Jurassic Unuk River Formation, Hazelton Group. These rocks consist of sandstone, wackes and shale overlain by lapilli-tuff of andesitic composition. The Brucejack fault and associated splay faults cut the country rock in a north-south to northwest direction. North of Brucejack Lake, the fault system is bounded on the east by rock of the Lower Jurassic Betty Creek Formation, Hazelton Group. A variety of Jurassic horn- blende syenites and alkali feldspar syenites occur in the area.

The 5.9 vein is part of a stockwork or sheeted vein zone occurring within weakly sericitic andesitic tuff-breccia. The 5.9 vein is between 20 to 100 centimetres thick and up to 40 metres in length. This vein assayed 185.14 grams per tonne gold and 18617.0 grams per tonne silver over 20 centimetres (Bridge, D., Melnyk, W., 1983). Other quartz veins in this area range in thickness from 0.5 to 2.0 centimetres and contain minor disseminated to semi-massive pyrite, sphalerite, tetrahedrite, galena and a trace of chalcopyrite.

Refer to Brucejack (104B 193) for details of related mineralization and work history.