The Mustang occurrence is underlain by dominantly metasedimentary rocks of the Hadrynian to Lower Paleozoic Snowshoe Group. In this area the Snowshoe Group comprises limestone, phyllite and quartzite.
Near the top of Mustang Mtn. recent road work Poschner Construction in 1987 has exposed copper-stained phyllitic quartzites. One sample assayed 0.11% copper (Assessment Report 16755).
See Tom Mountain (093H 077) for a discussion of the area work history.