COMPACT FELSPAR. 377 



The rocks of this character are always easily 

 recognized, even at a distance, by the white, 

 nearly pulverulent, surface which they assume 

 on exposure to the air. 



For the general definition of this rock, I may 

 refer to the several treatises on mineralogy in every 

 person's hands, where it is described among the 

 simple minerals, of to the description of its charac- 

 ters given in the thirteenth chapter of this work. 



The varieties which it affords are so few, and 

 so slightly different from each other, that they 

 scarcely admit of being distinguished by any 

 description or enumeration of characters. The 

 distinctions of colour are the most conspicuous. 



SYNOPSIS OF COMPACT FELSPAR. 



FIRST DIVISION. 



Simple. 



a. Massive, compact, with a smooth fracture. 



b. Schistose, with a similar fracture. 



This variety occurs in lona. 



c. Massive, with a granular or minutely 



uneven fracture ; appearing to be 

 formed, like granite, by a confused 

 crystallization. 



