CLASSIFICATION OF SEDIMENTARY ROCKS. 



785 



Following Nauniann and Hairy," the fragmental rocks are divided into 

 three orders — psephites ^yj<pog, a pebble), psammites (-^a^dg, sand), and 

 pelites (7tr{k6c„ clay). The psephites include the fragmental rocks which 

 contain abundant fragments coarser than peas. Frequently the matrix 

 of the psephites is psammitic. The psammites, following Rosenbusch, 6 

 are defined as including the sedimentary rocks which are composed of 

 particles under the size of peas and larger than dust. The pelites are 

 composed of the minute particles, from those of the size of dust down. 



The unconsolidated psephites, depending upon the coarseness, may be 

 called pebble, gravel, or bowlder deposits. Since the psephites are 

 unassorted material, the order includes but this one family and their 

 metamorphosed equivalents. 



The psammite order comprises three families — quartz sands, quartz- 

 feldspar sands, and ferromagnesian sands, and the metamorphosed 

 equivalents of each. 



The pelite order includes but one family — the muds, and their 

 metamorphosed equivalents. 



The foregoing classification may be represented in tabular form as 

 follows: 



Classification of sedimentary rocks. 



a As cited by Zirkel, F., Lehrbuch der Petrographie, Leipzig, 1893, vol. 1, pp. 493-504. 

 & Rosenbusch, H., Elemente der Gesteinslehre, Stuttgart, 1898, pp. 386-389. 



MON XIVII — 04- 



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