The Andy Lake showing area is underlain by northwest trending, steeply dipping belts of limestone, argillite, andesite and greenstone of the Carboniferous to Triassic Nicola and/or Harper Ranch groups which are intruded by diorite and hornblendite of the Triassic to Jurassic Heffley Creek pluton.
A 1.5-metre thick quartz vein contains sparsely distributed galena crystals and clusters, chalcopyrite and pyrite. Wallrock appears to be diorite.