ARGILLACEOUS SCHIST. 359 



G. Argillaceous schist with imbedded particles 

 of calcareous spar. 



Occurs in Galloway, and, as it is said, in 



some parts of the Alps. 



\ 



H. Argillaceous schist with imbedded felspar, in 

 crystals or fragments more or less rounded, and having 

 a porphyritic aspect. 



This singular variety is found in Isla and Jura. 



THIRD DIVISION. 



Of Argillaceous schist, with two or more in- 

 gredients. 



A. Argillaceous schist with quartz sand, and 

 mica. 



a. Schistose. 



b. Massive. 



These are also ranked under the comprehen- 

 sive term graywacke. When the quartz predo- 

 minates, they pass into micaceous sandstone. 



B. Argillaceous schist with quartz and felspar. 



C. Argillaceous schist with quartz, felspar, and 

 mica. 



These form other varieties of graywacke, and 

 are generally thickly fissile. They are found in 



