386 THOMAS L. WATSON 



than the granites, and they form the country rock into which the 

 granite was intruded. 



Exposures of the granite are in the nature of huge bowlders, 

 ledges, and flat-surface masses. Sections of the fresh and weathered 

 granite are seen to advantage in the cuts along the Seaboard Air- 

 Line Railroad to the east and west of Lilesville. 



It is a coarse-grained porphyritic biotite granite of gray color, with 

 pinkish and yellow tones characteristic in places. The groundmass is 

 medium coarse-textured, dark gray, granite, containing, as a rule, 

 much biotite. This is subject, however, to some variation. In the 

 railroad cut one and a half miles west of Lilesville the biotite has quite 

 a different occurrence and distribution in the granite from that of any 

 other exposure examined in the area. Here the biotite is usually in 

 sharp idiomorphic hexagonal plates, distributed through the rock as 

 single individuals and aggregates, which occupy distinct areas. 

 Elsewhere it occurs as irregular shreds crowded close together and 

 freely distributed through the groundmass. 



The phenocrysts are composed of potash feldspar, showing marked 

 cleavage development and twinned on the Carlsbad law. They are 

 usually of a pinkish hue, and may be either idiomorphic or allotrio- 

 morphic in outline; and, they contain usually some included biotite. 

 The ratio of phenocryst to groundmfss is variable, but will probably 

 average about one to three. 



The principal minerals are quartz, orthoclase, microcline, plagio- 

 clase (near oligoclase), biotite, chlorite, apatite, zircon, magnetite, 

 and a few other less common accessories. Microcline may fail in 

 some sections and be present in large proportion in others. Plagio- 

 clase is a constant constituent and is usually present in large amount. 



GRANITES OF THE PIEDMONT PLATEAU. 



GENERAL CHARACTERS. 



The Piedmont region in North Carolina is composed of a number 

 of geologic belts, approximately parallel to each other and crossing 

 the state in a general northeast-southwest direction. These belts 

 are composed, as a rule, of unlike rocks, probably of different ages. 

 A variety of granites are found within the limits of the Plateau region; 

 always biotite-bearing, with additional hornblende in some areas, 



