The area is underlain by andesite of the Upper Triassic Karmutsen Formation, Vancouver Group. The area to the west of the volcanics is intruded by a stock of the Early to Middle Jurassic Island Plutonic Suite. These plutonic rocks on Vancouver Island vary in composition from gabbro to quartz monzonite but are mainly granodiorite and quartz diorite. Dykes of quartz porphyry are also reported to cut the andesite.
The deposit consists of two vein types: 1) a mineralized lens-like quartz vein, on the east bank of the Moyeha River at its mouth and; 2) a composite vein system of numerous 5 centimetre (and less) wide veins (located about 400 metres east of the river deposit).
The vein located on the river bank was mined by an adit that, by late 1935, had been driven eastward for 19 metres. The vein is des- cribed as lens-like, varying from 2.5 to 20 centimetres in width, with an average strike of 140 degrees and a dip of 35 degrees south- west. The vein branches into a hangingwall and footwall vein; but 7 metres from the portal they join and continue as one vein which var- ies in width from 1 to 10 centimetres. The quartz is milky, somewhat vuggy, and contains small amounts of pyrite, chalcopyrite, sphaler- ite, galena, and free gold. A 15 centimetre chip assayed 51.43 grams per tonne gold and 17.14 grams per tonne silver (Minister of Mines Annual Report 1935). A sample, taken 12 metres from the portal, contained 304.57 grams per tonne gold (Geological Survey of Canada Memoir 204).
The host rock is a very platy porphyritic andesite. The attitude of jointing in the andesite is reported to be the same as that of the quartz vein.
The composite vein system is hosted by andesite, quartz porphyry and granite. The zone of veining is 115 metres long but the aggregate vein lengths are reported to total only 11 metres. The veins have an average strike of 160 degrees and dip of 25 degrees east. These veins typically carry only a little chalcopyrite and galena. At one showing, however, a 10 centimetre vein was found to contain an abundance of these sulphides. A 10 centimetre sample across this vein assayed 425.15 grams per tonne gold and 377.15 grams per tonne silver (Minister of Mines Annual Report 1935).
There are four years in which mining production was recorded: 1933, 1939, 1940 and 1941. From a total of 63 tonnes mined during these years, 5,070 grams of gold, 2,956 grams of silver, 212 kilo- grams of copper and 203 kilograms of lead were produced (Mineral Policy data).