GRANITES OF NORTH CAROLINA 



405 



QUARTZ VEINS. 



Quartz veins of small dimensions cut the granite in a number of 

 quarries ; usually, in the ones where pegmatitic intrusions are strongly 

 developed. They are not numerous in any of the openings, and, as a 

 rule, they will not measure more than a few inches across. Veins of 

 quartz of considerable dimensions are numerous over the crystalline 



Fig. 7. — Stone Mountain, Wilkes count_y, North Carolina. A granite residual. 

 Several others are shown in the distance on the extreme left of the view. 



area of the state, and they can be readily traced over the surface for 

 considerable distances by partially disintegrated outcrops and abund- 

 ant angular fragments which litter the surface. 



RELATIONS BETWEEN THE JOINTS IN THE GRANITE AND 

 THE DIKES OF BASIC ROCK. 



Referring to the direction in the strike of joints discussed on p. 23, 

 it will be observed that the planes of most of the joints lie in the north- 

 east and the northwest quadrants, respectively. Likewise careful 

 measurement and tabulation of the dikes of basic rocks show that the 



