Placer gold occurs almost exclusively in the gravels of the streams that drain the area underlain by the slaty schists of the Jurassic to Cretaceous Leech River Complex (Formation). Fairly coarse gold may be found in the gravels of virtually all these streams. The gold in the Recent gravel deposits has likely been derived from the numerous quartz veins that occur in the slaty schists. These veins are seldom more than small stringers and lenses a few centimetres wide and a metre or so in length. The only metallic minerals in the veins are a little pyrite or chalcopyrite and free gold. The veins are generally too small and too barren to be profitably mined.

The placer deposits were discovered in the 1860's and at that time were extensively worked. It is believed that over 3,000 men were engaged in placer mining at one time along Leech River. By 1876, it was estimated that 100,000 dollars worth of gold had been recovered. Later estimates place the actual value between 100,000 and 200,000 dollars (Holland, 1944). Signs of old workings are seen along the river upstream from the Sooke River, a distance of about 6.5 kilometres, to a point 1.5 kilometres beyond the first fork. According to G.M. Dawson the run of gold turned up the North Fork but rapidly diminished and ran out above the falls in the Devil's Grip. Between 1924 and 1945 a recorded 192 ounces of gold were recovered (Bulletin 28, page 16). Of the tributaries to Leech River, Martin's Gulch is notable for the gold that was found for a distance of 2 kilometres up from Leech River.

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 river. The gold recovered from the benches was mined either at: a) a depth of 3 to 5 metres and 3 metres above river level on a clay "false bedrock" of a low bench on the north side of the Leech River that extends 400 metres upstream from its junction with the Sooke River or; b) on the bedrock beneath the shallow overburden on a rock bench about 3 metres above river level that extends more or less continuously on one side of the river or the other, at least as far as the first fork in the river about 5 kilometres upstream from Sooke River. Nuggets varying in size from 15.6 to 31.1 grams have been recovered.