The Sombrio Placers, on the southwest coast of Vancouver Island near Sombrio Point, occur in a fairly level coastal area composed of sand, gravel and clay from 60 to 120 metres in depth. These gold placers are apparently the remains of a glacial delta deposited by glacial and postglacial rivers that drained southwestward through the Leech River valley. The east side of the delta is cut by Loss Creek, and the west side, up to 3 kilometres away, by the Sombrio River.

The Leech River fault stretches from west of Victoria westward along the Leech River and Loss Creek valleys to the coast near Sombrio Point. To the north of the fault the area is underlain by metamorphic rock of the Jurassic to Cretaceous Leech River Complex. To the south of the fault the rocks are mainly basalts of the Eocene Metchosin Volcanics. The gold is thought to have been derived from quartz veins and stringers known to occur in slate of the Leech River Complex.

The Spaniards first identified gold in the area in 1792; the name "Sombrio" is Spanish for colours. Elaborate camps and engineering works were constructed on the property from 1900 to 1930. Some production was reported to have occurred from 1907 to 1914 utilizing a 50-man monitor and sluice operation. Work continued on the deposit in the 1970's and 1980's. An estimate of the size of the deposit was given by Clapp as 155,000,000 cubic yards (Geological Survey of Canada Memoir 13, page 155).