Cannel coals are odd varieties of coal. They don't have the look & feel of ordinary coals such as lignite, bituminous coal, and anthracite. Cannel coals are lightweight, as all coals are, but are surprisingly tight and solid - they hold up to natural weathering pretty well, considering they're coals. They are not sooty to the touch, and have conchoidal fracture (smooth & curved fracture surfaces). Cannel coals lack the well-developed horizontal bedding & laminations seen in lignites and bituminous coals (see cross section view in 2nd photo below).
Not surprisingly, the differences in physical characterstics between cannel coal and other ranks of coal are due to the organic matter content. Cannel coals are composed principally of fossil spores (sporinite phytoclasts). Garden-variety coals are composed principally of a mix of altered fragmented plant debris that was originally woody tissue, leaves, bark, fungi, and spores. Cannel coals are generally interpreted to have formed in pond, lagoon, or channel facies within a larger coal swamp setting.
Cannel coal (bedding plane view; 8.5 cm across).
Cannel coal (cross-section view; field of view 5.2 cm across)