LOWEST RED SANDSTONE. 411 



D. Quartz sand with carbouat of lime and clay : 

 argil lo-calcareous sandstone. 



a. Gravelly. 



b. Arenaceous. 



These vary in colour according to the tints 

 of the clay. When the quartz is very fine and 

 in small proportion, they pass into calcareous 

 shale or marie slate. 



E. Quartz sand with mica, or with mica and clay : 

 of various degrees of fineness. 



a. The mica irregularly interspersed : 



massive. 



b. The mica disposed in a parallel manner, 



often in separate laminae: schistose, 

 and splitting more or less perfectly. 

 Schistose sandstone. 



F. Quartz sand with indurated or schistose clay. 

 This may equally be enumerated under the 



head of argillaceous schist, (graywacke) ; but it 

 occurs as a transition from sandstones of a de- 

 cided character, and is associated with them. 



G. Quartz sand, with sand from the wearing of 

 trap rocks. 



Other varieties occur from the occasional in- 

 termixture of other minerals, or from the exist- 

 ence of a greater number of ingredients ; but 



