VOLUME XXVIII NUMBER 3 



THE 



JOURNAL OF GEOLOGY 



APRIL-MA Y ig20 



COMPILATION AND COMPOSITION OF BITUMINOUS 



COALS 



REINHARDT THIESSEN 



Bureau of Mines Experiment Station 

 Pittsburgh, Pennsylvania 



A seam or bank of ordinary bituminous coal is readily seen to 

 be stratified; likewise a block or chunk of the same is seen to be 

 highly laminated, and found to be compiled of various layers and 

 sheets of coal differing from one another in color, texture, and 

 fracture, and varying greatly in thickness.' 



There are generally recognized and described by various authors 

 two kinds of coal with respect to its texture: compact coal 

 and mineral charcoal or mother-of-coal. The former forms by 

 far the larger and the more important part, while the latter forms 

 but a very small, but on account of its nature a conspicuous part of 

 the coal. The mineral charcoal will be considered as unimportant 

 and only incidentally in this paper. 



In the compact coal, in general, two kinds of layers are recog- 

 nizable, apparently alternating and standing in sharp contrast to 

 one another. The one is of a jet-black, pitchy appearance, more 

 compact, and breaking with a concoidal fracture. The other is 

 somewhat grayish in color, of a dull appearance, less compact, and 



^ The figures mentioned in this article are arranged on plates at the end of the 

 article. See Explanation of Plates, p. 206. 



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