Pegmatite dykes and pipe-like masses of pegmatite are numerous along the northwest shore of Douglas Channel between Hartley Bay and Helen Point. The area is underlain by the southeast end of the Ecstall Pluton consisting of granodiorite and quartz diorite.

The pegmatites are composed of microcline, orthoclase, oligo- clase, albite, perthite, micropegmatite, quartz, and biotite. The microcline, orthoclase, and biotite form crystals up to 45 centimetres in size.