158 DOMAIN II. SILICEOUS. 



STRUCTURE I. COMMON. 



Aspect 1. Common foliated. This rarely forms 

 entire mountains, but such have been discovered 

 in Siberia. When it forms mountains it is gene- 

 rally white. 



Aspect 2. Granular. Ptocks of a fine white 

 granular felspar, resembling statuary marble or 

 dolomite. Sauss. 2144. 



Aspect 3. Unctuous. Saussure, 1304, de- 

 scribes what he calls felthspath gras, or unctuous 

 felspar, as having a visage more oily and trans- 

 lucent than common felspar : the fracture rarely 

 laminar; and the plates, when perceivable, not 

 being level, but often convex, so that almost all 

 the fractures are generally conchoidal. It is harder, 

 and less fusible, than the common. 



STRUCTURE II. MINGLED. 



This division may justly comprise numerous 

 rocks and entire mountains, consisting of felspar 

 interspersed with a little mica or quartz, or a few 

 garnets ; the preponderance of the felspar being so 

 great that they cannot be considered as granitels. 



