Magnesite occurs in outcrop and as float in overburden at several locations in railway cuts along the southwest side of Lac La Hache.
The Lac La Hache area is underlain by alkaline olivine basalt plateau lavas of the Miocene to Pleistocene Chilcotin Group overlain by till and glaciofluvial deposits of Pleistocene age. The magnesite is exposed as highly weathered sedimentary material immediately underlying the plateau basalts and it also occurs as short, narrow veinlets cutting the basalts.
Samples of magnesite are dense, fine-grained and white. Material associated with the contact zone is yellowish and highly decomposed but effervesces in cold dilute acid and is quite plastic when wet. The largest observed vein was 30 centimetres thick.
A sample submitted to the Ministry of Energy, Mines and Petroleum Resources in 1917 contained 70 per cent MgCO3, 27 per cent CaCO3 and 2 per cent iron.