coal lithotype

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coal lithotype Type of coal, the nature of which depends on original plant structure. Clarain has a semi-bright, shiny lustre, is finely laminated, with smooth or irregular fracture, and is banded parallel to bedding. Durain is grey to brownish-black, banded, dull, with a granular and rough surface; harder than vitrain and more common. Fusain is sooty black, with silky lustre; it is fibrous and friable like charcoal, and occurrences are usually thin and impersistent. Vitrain is black, with brilliant, glassy lustre, conchoidal fracture, and cubic cleavage. It is clean and structureless, and occurs in thin bands or lenses.