378 THOMAS L. WATSON 



identical. With one exception, the two textures grade one into the 

 other, representing different textural phases of the same rock-mass. 



Porphyritic granites have wide distribution over the state in asso- 

 ciation with the even-granular phases of the rock. The most impor- 

 tant areas are: (i) The Wadesboro-Rockingham area to the east of 

 Charlotte and near the South Carolina line, extending over contiguous 

 parts of Anson and Richmond counties. Over parts of this area the 

 feldspars are colored a rich olive-green, representing apparently a 

 superficial phenomenon caused by some form of surface alteration. 

 A second difference noted is in the distribution and character of the 

 biotite, which occurs in hexagonal plates of single or grouped individ- 

 uals occupying distinct areas. (2) The Gastonia area in Gaston 

 county, west of Charlotte. (3) The Mooresville area in Iredell 

 county. (4) The Cabarrus county area, three miles southwest of 

 Concord; and a second area in the same county in the vicinity of 

 Landers station on the Southern Railroad, to the north of Concord 

 and near the Rowan county line. The porphyritic rock occurring 

 three miles southwest of Concord is quite different in appearance from 

 that of any other area of porphyritic granite known in the state. 

 Here the rock is uniformly coarse-textured and largely feldspathic, 

 composed of large bluish-gray feldspars without pronounced crystal 

 outline. The rock contains hardly more than a trace of groundmass, 

 but is made up chiefly of the large feldspars wrapped about each other 

 and closely interlocked. Biotite in small irregular shreds is one of 

 the chief minerals in the scant groundmass. (5) The Salisbury area, 

 which forms one of the most extensive belts in the state and is traced 

 over parts of Rowan, Davie, and Forsyth counties. Smaller and less 

 important areas of similar porphyritic granite have been noted in 

 several other counties in the state. 



Excepting the area three miles southwest of Concord in Cabarrus 

 county, the porphyritic granite of the different areas mentioned above 

 is closely similar in color, texture, and mineral composition. The 

 groundmass is usually a medium-coarse gray granite composed of 

 feldspar, quartz, and biotite. Some variation in the amount of the 

 last constituent, biotite, is noted from place to place, resulting in a 

 corresponding variation of color from light to dark gray. The 

 porphyritically developed mineral is potash feldspar. As a rule, 



