The Chilliwack River occurrence area is underlain by Jurassic-Triassic Cultus Formation metasediments comprised mainly of sandstone and pelite. To the west is a high angle, steeply dipping fault which appears to have brought older crystalline gabbros and serpentinites over younger metasedimentary Cultus Formation argillite and pelite.

Brittle, harsh asbestos fibres, ranging up to 4.8 millimetres in length, occur in scattered veinlets 2.0 kilometres southwest of the confluence of Nesakwatch Creek and the Chilliwack River.

Monger reports that this serpentinite, of Paleozoic and/or Mesozoic age, contains discontinuous veins of chrysotile asbestos throughout the rock (GSC Paper 69-47).