376 THOMAS L. WATSON 



ite is extensively developed in many places, within the limits of the 

 Piedmont Plateau, and it forms over many parts of the plateau one 

 of the dominant rock types. The distribution of the principal gran- 

 ite areas of the state is shown on the accompanying map. 



Over all parts of the state the rocks are profoundly decayed from 

 weathering and, as a rule, are buried under a deep mantle of loose 

 residual decay. Notwithstanding the extensive decay of the rocks, 

 exposures of the moderately fresh granite are comparatively numerous 

 and assume oftentimes very large dimensions. The granite forms 

 unreduced residuals or ridges, as shown in Fig. 7, and it is further 

 exposed in bowlders and ledges and flat-surface masses, both along 

 the stream courses, and more or less remote from the streams on the 

 interstream areas. (Figs. 2 and 3.) 



Numerous quarries have been worked in the outcrops of granite 

 throughout the state, and the stone has been used for all purposes for 

 which granite is ordinarily adapted. 



TYPES OF THE GRANITES. 



Based on texture and structure three types of the granitic rocks are 

 distinguished: (i) the massive even-granular (normal) granites; (2) 

 the porphyritic granites; and (3) the banded or schistose granites — 

 granite-gneiss. Field and laboratory study develops close similarity 

 in the three types in mineral composition, and, with one exception, 

 the even-granular and porphyritic textures represent different phases 

 of the same rock-mass. Moreover, the granite-gneisses differ essen- 

 tially from the massive granites, from which they have been derived, 

 only in the pronounced schistose structure subsequently induced by 

 pressure-metamorphism. 



NORMAL GRANITES. 



The even-granular granites have wide distribution, and they 

 compose largely the bulk of the granites occurring in North Carolina. 

 As a rule, they vary from fine- to medium-textured rocks, rarely 

 coarse, and are of pink to gray color. With only a few exceptions, 

 light to medium and dark gray is the prevailing color of the granites. 

 Variation in structure is from massive to schistose rocks. They are 

 mixtures of orthoclase and plagioclase feldspars and quartz, with a 



