The Lillyburt occurrence is located in the Flathead Valley graben structure and is characterized by small- and large-scale gravity faulting. The roughly east trending Flathead normal fault is the predominant structure in the area (1200 metres displacement near Flathead townsite). Associated with it and subparallel to the main fault system are several strike-slip and normal faults. The southern margin of the property is defined by a large-scale gravity fault while the western margin consists of the Squaw thrust.
Within the major structural block, the coal-bearing strata are folded into an open asymmetric, east plunging syncline.
Between 6 and 10 coal seams ranging in thickness from 0.1 to 25 metres occur in the Jurassic-Cretaceous Mist Mountain Formation (Kootenay Group) (300 metres) interbedded with deltaic and fluvial claystone, siltstones and sandstones. Seam E, the uppermost of the five economic seams in the sequence, consists of seams less than 1 metre thick separated by shale and siltstone partings. Seam D averages 1 metre thick and is not present on the east half of the south limb of the syncline. Seam C is the thickest on the property (10-15 metres) and although otherwise clean, contains a 13-metre split on the east end of the south limb. Seam B is 1 to 2 metres thick, shaly and commonly contains a siltstone parting. Seam A overlies the Morrissey Formation sandstone, varies from 2.5 to 8.5 metres thick and may be quite shaly.
Volatile matter increases up section from an average 26 per cent in seam A to 32 per cent (dried, ash free) in seam E. Free Swelling Index values are below 2.0 in seams A, B and C. Raw ash content averages 40 per cent and sulphur is low, 0.3 to 0.5 per cent. The coal is medium volatile bituminous in rank.
Total indicated resources in the east block of the property are estimated to be about 130 million tonnes. Geological reserves are calculated to be 24.8 million tonnes (Coal Assessment Report 405).
The Lillyburt coal deposit is in the Flathead Mineral and Coal Reserve established in 2010; no tenure acquisition, exploration or mining activities are permitted.
