The Mount Beirnes West coal occurrence is a cluster of seven coal showings that were identified, trenched and sampled by Dawson and Ryan in 1991 (Geological Survey of Canada Open File 2555). The showings lie within a 1 kilometre radius of Trench BB90023 and are located on an unnamed alpine ridge about 12 kilometres west of Mount Beirnes approximately 139 kilometres north-northeast of the community of Stewart. The Nass River is about 8 kilometres west of the occurrence.

The Mount Beirnes West coal showings are hosted by the Lower Cretaceous Groundhog-Gunanoot assemblage of the Upper Jurassic-Lower Cretaceous Bowser Lake Group (Geological Survey of Canada Open File 5735), which includes sandstone, siltstone, carbonaceous and calcareous mudstone, with minor conglomerate and coal. Plant fossils are common and include in situ trees.

The Mount Beirnes West coal showings are in the Groundhog coalfield in the Bowser Basin and occur on the western flank of the Beirnes synclinorium. Strata are tightly folded into closely-spaced anticline-syncline pairs. Fold axes strike about 315 degrees (Geological Survey of Canada Open File 5735).

Coal rank ranges from semi-anthracite to anthracite. Vitrinite reflectance values range from 2.53 to 3.33 per cent RoMax.