The McQuillan vein is located 600 metres southeast of the Gillespie vein (092F 082) and the Havilah mine workings, about 20 kilometres southeast of Port Alberni.

The area is underlain by Devonian Sicker Group volcanic rocks (Duck Lake Formation). These are cut by a body of coarse-grained hybrid diorite of the Early to Middle Jurassic Island Plutonic Suite. A north trending fault bounds the diorite to the west and cuts andesite to the north of the diorite.

The McQuillan vein and the adjoining Alberni vein to the south, occur along a shear zone which cuts andesite, diorite and Tertiary quartz-feldspar porphyry. The shear zone trends 020 degrees for about 80 metres, dips 70 degrees east and is about 5 metres wide. Quartz lenses along the shear contain pyrite, sphalerite, galena and lesser chalcopyrite and arsenopyrite.

A 60 centimetre sample of a vein assayed 5.5 grams per tonne gold and 20.6 grams per tonne silver (Minister of Mines Annual Report 1936).

From 1999 through 2002, Mandalay Resources completed programs of prospecting and rock and soil geochemical surveys on the King claims.