The western end of the Alert Bay Volcanic Belt is now approximately 80 km (50 mi) northeast of the Nootka Fault, which separates the Explorer and Juan de Fuca plates.

[5] Although commonly referred to as andesite, by chemical composition the Haddington Island volcanic rocks are in fact dacite.

[6] The rock has a very fine grained to aphanitic texture, and has a light blue-grey to a warm brown-grey range in colour.

[6] Small, 1–2 mm plagioclase phenocrysts are distributed through the rock mass, and form approximately 1% of its volume.

[6] The grey to bluff andesite on Haddington Island is considered by many to be British Columbia's finest building stone because it is easily profiled and carved.