any of the numerous microscopically recognizable, individual organic constituents of coal with characteristic physical and chemical properties. Macerals are analogous to minerals in inorganic rocks, but they lack a definite crystalline structure. Macerals are coalified plant remains preserved in coal and other rocks. They change progressively, both chemically and physically, as the rank of coal increases. (Coal rank is a measure of a coal's degree of metamorphism expressed as its position in the lignite-to-anthracite series and is primarily based on decreasing volatile matter content and increasing carbon content.)
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