The area lies within the Shuswap Metamorphic Complex along the eastern margin of the Frenchman Cap Dome. The core of the dome is mantled by an unconformably overlying succession of meta-sedimentary rocks consisting of calc-silicate gneiss, quartzite, hornblende gneiss and marble.

A high accumulation of garnet and kyanite is reported to occur in the alluvial fan of Fortynine Creek, at its confluence with the Columbia River (Personal Communication, Z.D. Hora, 1998).