The country rocks near this prospect are mainly gray pelitic phyllite and subordinate andesitic or basaltic metavolcanic rocks that are intruded by Cretaceous stocks, sills, and dikes of feldspar-porphyritic granodiorite, and by small metadiorite plutons of undetermined age (Berg and others, 1988). The strata were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time, and, near some of the granodiorite contacts, subsequently contact metamorphosed to hornblende hornfels (Berg and others, 1988; Brew, 1996, p. 27). The premetamorphic age of the metapelite-metavolcanic unit is unknown. Berg and others (1988, p. 17) noted its resemblance to Upper Jurassic to mid-Cretaceous marine flysch and volcanic rocks on Annette and Gravina islands, but assigned it an undivided Mesozoic or Paleozoic age. Near Coon Cove it structurally overlies faunally-dated Permian and Triassic rocks.