The region is underlain by the Coast Plutonic Complex, consist- ing of pre- to post-kinematic quartz diorite to granodiorite batho- liths intruded into Paleozoic to Mesozoic metasedimentary and meta- volcanic rocks. Younger supracrustal assemblages overlying deformed rocks include the (?)Cretaceous Gambier Group and Tertiary Bella Bella Formation volcanic rocks.
The Elcho Harbour graphite showing is underlain by gneiss of presumed Paleozoic age in which a zone of metasedimentary (amphibolite facies) rocks occurs. These gneisses and schists occur within a large foliated quartz diorite batholith. The occurrence, reported to be a large deposit of disseminated graphite consisting of minute, lustrous, dark steel grey scales and scaly layers, may occur within the metasedimentary rocks. The location given is not precise and no other geological information is available for the occurrence.