The Privateer P4A vein 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 area's gold-quartz veins. Bedded rocks are predominantly northwest striking, southwest dipping, and anticlinally folded about a northwest axis.

The P4A vein strikes 070 degrees and dips 75 degrees north, following a 10-metre wide fracture zone in andesitic pyroclastics of the Bonanza Group. The vein is to 20 centimetres wide but averages about 7.5 centimetres and is often lensy. The quartz gangue contains varying amounts of pyrite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite and coarse calcite. Gold values to 19.9 grams per tonne were obtained from massive pyrite. A sample of pyrite-sphalerite galena with vein quartz assayed 62.4 grams per tonne gold, 178.3 grams per tonne silver, 0.14 per cent copper, 5.36 per cent lead and 2.77 per cent zinc (Bulletin 27, page 71). The vein is located 0.7 kilometres west of the Privateer mine (092L 008).