At the BJ occurrence mineralization occurs in the northeast contact zone of an Early to Middle Jurassic Island Plutonic Suite (formerly the Island Intrusions) body, and rocks of the Devonian Nitinat Formation, Sicker Group. The rock immediately adjacent the stock is black amphibolite cut by many small granitic dykes and pegmatitic vein-dykes. It passes northeastward through migmatite to somewhat schistose and recrystallized pyroxene basalt (Nitinat Formation). To the southeast the basalt is in contact with gabbro (informally known as the Mount Hall Gabbro) which, like the amphibolite, is cut by many small granitic dykes.

The amphibolite and migmatite contain wispy zones, 30 to 60 centimetres wide, of disseminated and seam pyrite accompanied by less chalcopyrite. These zones are exposed only in one place, and only scattered occurrences of sparsely disseminated pyrite were found in the basalt and gabbro.

A quarry was reported to have been opened up in the contact zone in order to provide rock-facing for dams at each end of Holland Lake.