Coal is found in sedimentary rock formations such as those of the Rocky Mountains in southern Alberta and British Columbia. It was formed from deep layers of plant materials dating from the Lower Cretaceous period which, over millions of years, and under great pressure, slowly formed the rock-like deposits of coal.

Faulting, folding and erosion all complicated the geology of the Crowsnest region making it difficult to determine where the coal seams were deep within the mountains. Often the seams were at steep angles and were broken and difficult to trace through the mountains. Some seams were deep underground. Others, which were the most easily mined, were generally flat and were exposed on the sides of the mountains with the seams running into the mountain sides. The mines at Coal Creek near Fernie worked a generally flat seam exposed on both sides of the valley.

In some mines, seepage or underground streams could make the workings very wet and water had to be pumped out of the mines. However, in some seams where there was little moisture, it was necessary to install sprayers to keep the airways and main tunnels (gangways) damp to reduce dust and gas.

The coal fields were eventually determined to extend through the Morrissey-Fernie area along the Elk River, north to Natal and Michel and to recur in patches, such as the major deposit at Corbin, throughout the mountainous area to the south including the upper Flathead River valley. Other major deposits were discovered farther up the Elk River at Harmer, Line Creek, Greenhills and Fording and a number of these were developed as major mines in the late 1960s and 1970s. Other major outcroppings of the seams occur on the Alberta side of the Crowsnest Pass at the major historic coal mining towns.

The Crowsnest Pass coal field is an immense deposit of coal containing millions of tonnes of coal in different seams. At Corbin, near the summit of the Pass, the coal seam mined in the early 1900s was up to 200 feet (61 m) thick although in places it was divided by some layers of shale. At Michel by the mid 1920s, eleven coal seams were know with a total thickness of about 110 feet (34 m) of coal.