The Mica (Bigmouth) occurrence is described as being located in the headwaters of the west fork of Big Fish Creek, 3 kilometres north of Groundhog Basin.

The area is underlain by metasedimentary rocks interlayered with mafic volcanic rocks of the Cambrian to Devonian Index Formation (Lardeau Group). The metasediments consist of quartzites, schists, phyllites, calcareous schists, carbonates and fine clastic rocks. The metavolcanics are tholeiitic flows and mafic tuffs metamorphosed to greenstone and chloritic phyllite.

Locally, a lensoidal, 1 by 30 metre, vuggy, quartz-pyrite vein hosts coarse galena with minor sphalerite and chalcopyrite. The vein is hosted by a spotted quartz-biotite pelite and greenish quartzite sequence and is oriented parallel to layering and foliation.

In 1982, grab samples of the vein assayed up to 2.52 per cent lead, 71.8 grams per tonne silver and 0.4 gram per tonne gold (Property File - G. Gibson [1983-05-01]: Final Report on the Wood River Project - 1982).

In 1982, E & B Explorations prospected the area as the Mica claims.