The Chemainus River flows east from its headwaters on Mount Whymper to Mount Sicker and then northeast through Copper Canyon to its mouth on the east coast of southern Vancouver Island.

The area is within the Cowichan uplift and is located in an area underlain mainly by andesitic to rhyolitic volcanics of the McLaughlin Ridge Formation (Sicker Group). The local stratigraphy is disrupted by folding, faulting (pre-Triassic as well as Tertiary) and intrusions of gabbro and diabase sills and dikes (informally called the Mount Hall Gabbro) that are coeval with the Upper Triassic Karmutsen Formation (Vancouver Group).

Placer gold is reported in the lower Chemainus River, stretching over 5 kilometres from Copper Canyon down to the large south eastern turn in the river. The gold is likely related to known lode deposits on Mount Sicker such as the Lenora (MINFILE 092B 001) and Tyee (MINFILE 092B 002) occurrences.

Placer gold has also been reported in the western head waters of the river, near El Capitan Mountain.

The topography shows that the stream has cut down through the bedrock, leaving a series of gravel- covered benches. It appears that most of the gold was derived from bars or in crevices in the bedrock of the river bed, or from benches along the side of the creek.