Modern Concepts of the Physical Constitution of Coal

Abstract

The modern concepts of the physical constitution of coal involve megascopic recognition of four primary-type coals — vitrain, clarain, durain, and fusain—and subtypes due to variations of a microscopic order in the physical constitution of the primary- type coals. Most coal beds consist of composite associations of the primary-type coals. The technique of coal description has, in general, not kept pace with the technique of type differentiation. The validity of type classification has not been fully established by chemical evidence, which evidence, however, is strongly suggestive that the differences are real. The practical significance of the variations in coal lies in the fields of coal classification, coal preparation, and coal processing, including hydrogenation.