276 MICACEOUS SCHIST. 



SYNOPSIS OF MICACEOUS SCHIST. 



FIRST DIVISION. 



Consisting 1 of mica and quartz. 



FIRST SUBDIVISION. Simply laminar, 

 or foliated. 



A. Formed of mica, continuously laminar, with 

 scarcely a discernible proportion of laminar quartz. 



A variety of considerable beauty arises from 

 the mica occasionally presenting two distinct 

 colours, as white and black, or greenish and 

 grey. Many of these specimens appear to con- 

 sist of mica only, but I believe that quartz is 

 never entirely absent. * 



B. Formed in the same manner, but the propor- 

 tions of the ingredients reversed. 



In this case, the cross fracture presents the 

 aspect of quartz rock, while the mica alone is 

 visible in the laminar fracture. 



C. The continuity of the mica becoming inter- 

 rupted, and the quartz becoming granular. 



