At Hamilton Lake, four major coal seams which average 3.6 and 2.6 metres (clean coal) in thickness, in Block A and Block B respectively, are present in the Upper Cretaceous Comox Formation, Nanaimo Group (approximately 91 metres thick) interbedded with shale and sandstone. Blocks A and B are areas which contain coal seams mineable by open cut mining methods. The coal in the deposit area is classified as high-volatile bituminous A and can be characterized as a semi-soft coking coal. Some of the seams are split as a result of faulting and stress. The direction of sedimentation is towards the southeast and individual seams may thin and splay in this direction.
Indicated resources are 8,522,204 tonnes and 2,602,469 tonnes in Blocks A and B respectively. Total reserves are 11,124,673 tonnes with an overburden ratio of 7.38:1 (Coal Assessment Reports 49, 56).
The structure in the area is dominated by northwest and north- east trending normal faults which down fault the Comox Formation sediments against the older Upper Triassic Karmutsen Formation volcanics. A major north trending fault extends from Brown's River through the east boundary of Comox Lake and south through Allen Lake to the Trent River. Beyond this a downthrow of 61 metres occurs. The strata generally strikes west-southwest to northwest and dips predominantly north.
Combined Measured and Indicated resources are 8,512,000 tonnes in Blocks A and B respectively (Coal Assessment Report 887).