Up to 20 coal seams occur in the Jurassic-Cretaceous Mist Mountain Formation (Kootenay Group) in the Tobermory Ridge occurrence area. The coal is high volatile bituminous in rank and the seams are interbedded with sandstone, siltstone and shale. Five seams are of mineable thickness.

The coal-bearing strata occur on either side of the Alexander Creek syncline which trends northwest in the area. The syncline is faulted to the south in the vicinity of the Cadorna Creek depression and to the north by an east-west bend in the predominantly north-northwest trending, west dipping Borgeau thrust fault.