Cannel coals: Implications for classification and terminology

Cannel coals are tough, massive coals with a dull luster that break with an even, compact grain and conchoidal cross fractures. Historically, cannel coals were of significant economic and social importance during the early industrialization of the USA. They were the source for a sophisticated petrochemical industry and a fuel source for heating, gas making, coke making and oil generation. Petrographic data, proximate analysis and ultimate analysis data were obtained for 68 cannel coals from Kentucky to decide how well the cannel coals fit the generally-accepted definitions of a cannel coal. Four maceral assemblages were found-sporinite with abundant medium-grained vitrinite and inertinite, sporinite with abundant fine-grained vitrinite and inertinite of which micrinite is abundant (bituminite may be present), alginite with abundant fine-grained vitrinite and inertinite, and alginite and bituminite with minor vitrinite and inertinite. Volatile matter and H/C ratios are highest for those samples with abundant liptinite with a sample from Breckenridge having the highest value of each. Five samples were analyzed by the Rock-Eval method. The S₂ and HI indices show that the coals would make excellent source rocks. Discrepancies between the values for the five samples are related to maceral composition and there may be a good correlation between source rock potential and importance as a feedstock for synthetic crude oil production in the 1800s. The maceral composition of the microlithotypes is related to the environment of deposition. Coal composed of assemblage (i) formed in humic peat swamps in which unusually large numbers of spores were introduced, possibly because of unusual, climatically controlled reproductive cycles. Coals composed of assemblages (ii) to (iv) formed as sapropelic coals in lakes at some stage of peat swamp development.