The Brown Bomber showing lies in the Zeballos gold camp which is underlain by the Lower Jurassic Bonanza Group. The Bonanza Group is an island arc sequence consisting of basaltic to rhyolitic volcanic rocks. Conformably underlying the Bonanza Group rocks are limestones and limy clastics of the Quatsino and Parson Bay formations, and Karmutsen Formation tholeiitic basalts, all belonging to the Upper Triassic Vancouver Group. Dioritic to granodioritic plutons of the Zeballos intrusion phase of the Jurassic Island Intrusions have intruded all older rocks. The Zeballos stock, a quartz diorite phase of the Eocene Catface Intrusions, is spatially related to the areas gold-quartz veins. Bedded rocks are predominantly northwest strik- ing, southwest dipping, and anticlinally folded about a northwest axis.

The Brown Bomber vein in 1940 was explored for 30 metres by open cuts. The vein strikes 057 degrees and dips 80 degrees north. It shows rusty vein material, gouge and a 5 centimetre quartz stringer carrying finely disseminated pyrite and sphalerite. It is located in quartz diorite of the Catface Intrusions.