1 90 MINERALOGY AND LITHOLOGY. 



ites which contain both feldspar and quartz, and sienites which contain 

 only feldspar. The granites are then further sub-divided, according as 

 to what mineral is present as the characteristic accessory, and the sien- 

 ites are likewise sub-divided. Other authorities, considering the distinc- 

 tion between hornblende and mica as fundamental, divide them into 

 granites which are micaceous, and sienites which are hornblendic. In 

 this work the first method of sub-division is adopted, and the following 

 kinds of granitic rocks have been identified in the state : 



Granite. 



Muscovite granite. 



Muscovite biotite granite. 



Biotite granite. 



Mica hornblende granite. 



Hornblende granite. 



Chlorite granite, or protogene. 



Granitell, or granite with no accessory. 



Granite of veins. 



Siciiite. 



Augite sienite. 

 Hornblende sienite. 



Granite. 



Although our granites can be sub-divided according as they contain 

 muscovite, biotite, hornblende, or chlorite as the characteristic accessory, 

 yet the dividing points between these sub-species can only be arbitrarily 

 assumed, since most of our granites contain two of these minerals, many 

 contain three, and some contain all four. It is therefore the predomi- 

 nance of one or the other that forms the species ; and the intimate 

 blending of these species causes them, together with the granitell, to 

 form one well defined rock group, all the members of which are in com- 

 mon usage called granite. As the quartz and feldspar are light-colored 

 minerals, the accessories are rendered very prominent, and determine 

 to a great degree the color of the rock. The granites that contain no 

 accessory or muscovite are white; biotite and hornblende granites are 



