INTEKMEDIATE CHARACTER OF APPALACHIAN GRAXITES 



19 



It ^vill be observed from the preceding table that all of the Virginia rocks 

 fall in class I, persalane; and order -i, Brittanare. The first five of the 

 seven fall in rang 2, domalkalie; and subrang 3, sodipotassic, and are 

 termed toscanose. The other two (VI and VII) fall in rang 3, alkaliealcic ; 

 VI falls in subrang 3, sodipotassic, and is termed amiatose; VII falls in 

 snbrang 3-1, between sodipotassic and dosodic. and is intermediate between 

 amiatose and yelloivstonose. 



jSToeth Carolina. 



Mineral composition. — The iSTorth Carolina acid plutonic rocks contain 

 the same essential and accessory minerals as those of Maryland and 

 Virginia. Hornblende as a chief accessory mineral is known to occur in 

 the rocks of only two localities. With the exception of these, the rocks 

 of the State are biotite granites, in which very subordinate muscovite 

 associated with biotite may occur. The rocks of the Dunn's Mountain 

 and Wilson areas are essentially mixtures of feldspars and quartz, with 

 scant biotite as the third principal mineral. Based on texture and structure 

 the usual three types of acid rocks are distinguished. 



Chemical composition. — The table of partial analyses below shows the 

 range in silica, lime, and alkalies in the N"orth Carolina rocks. 



F. Table of partial analyses of North Carolina granites. 



I. Dunn's Mountain gray granite, near Salisbury, Rowan county, N. C. W. M. 



Thornton, Jr., analyst. 

 II. Dunn's Mountain pinlc granite, near Salisbury, Rowan county, N. C. W. M. 



Thornton, Jr., analyst. 

 III. ilt. Airy, Surry county. North Carolina. W. M. Thornton, Jr., analyst. 

 IV. Granite three miles north of Gtold Hill, Rowan county, N. C. A. S. Wheeler, 



analyst. 

 V. Raleigh, Wake countv, North Carolina. Bull. No. 2, N. C. Geol. Survey, 



1906, p. 32. 

 VI. Mooresville, Iredell eoiuitv, North Carolina. Bull. No. 2. N. C. Geol. Survey, 



1906, p. 84. 



The range in silica in the Xorth Carolina rocks is great, from 66.01 

 per cent, to 77.19 per cent., with a higher average, 72.64 per cent., than 



