This communication extends the method of classifying carbonaceous minerals already introduced in order to include the three components of common coal. The existence of the three constituents has long been recognised, but their close study, and the nomenclature now generally accepted, date from 1919, when Dr M. C. Stopes described their salient characteristics in a paper to the Royal Society. In that paper she gave the name durain to the hard, lustreless constituent, that of vitrain to the lustrous part, and borrowed the French miner's name fusain for the charcoal-like material commonly found between the bands of a coal seam. A bright variety, called clarain by Dr Stopes, is now usually regarded as a blend rather than as a separate substance, and may be disregarded in a classification such as this.