There are several placer gold deposits along the Cottonwood River. The deposits are located in benches ranging in height from about a metre to several metres above the present course of the river. The gold is derived from interstadial and possibly pre- glacial deposits. The ultimate source of the gold may have been the auriferous veins of the Barkerville terrane from which the Cottonwood River drains. The pre-Tertiary geology of this area consists of mafic volcanic and sedimentary rocks of the Upper Triassic to Lower Jurassic Nicola Group of the Quesnellia terrane.

Gold from the Mary Creek placer deposit was won from pay gravels a few centimetres to a few metres thick. The varying degrees of wearing of the gold particles suggest both proximal and distal sources.

Production was from a channel on bedrock with an average thickness of 1 to 7 metres across a channel width of 45 to 60 metres. The channel extends at least 480 metres. The average grade was 2.74 grams per cubic yard or about $38 to $42 per cubic yard (George Cross Newsletter #117, June 18, 1991).

Supergene leaching of gold, dispersed by Tertiary deep weathering and followed by Cenozoic erosion, is the likely explanation for the occurrence of coarse gold nuggets in Quaternary sediments (Exploration in British Columbia 1989, page 147).