388 THOMAS L. WATSON 



plagioclase, in the form of inclusions in the larger potash feldspar 

 individuals developing micropoikilitic structure. Microcline nearly 

 equals orthoclase in quantity, and plagioclase is hardly less than both. 

 Carlsbad twinning is sometimes observed in the feldspar. 



Biotite is brown in color, strongly pleochroic, and is largely altered 

 to chlorite and some epidote. An occasional shred of muscovite is 

 intergrown with the biotite. The other accessory minerals present 

 no noteworthy features. 



The larger feldspar and quartz individuals are partially or entirely 

 surrounded by finer mosaics of the same minerals, denoting peripheral 

 shattering from dynamic forces. Strained shadows in the minerals 

 are further characteristic of the same pressure effect. 



In the northern part of Wake county, in the vicinity of Rolesville, 

 a light pinkish biotite granite occurs, which differs from the Raleigh 

 granite in the hand specimen, but does not differ essentially in mineral- 

 ogy. Plagioclase is very variable, equaling in some sections the potash 

 feldspar and nearly faiHng in others. Orthoclase and microcline are 

 in nearly equal proportion. Small irregular areas of micrographic 

 intergrowths of quartz and feldspar are quite abundantly distributed 

 through the thin sections. 



The Grey stone area. — The Greystone quarries are among the largest 

 in the state. The typical Greystone granite is medium gray in color, 

 of pronounced schistose structure, and in texture varies from fine- to 

 medium-grained. More or less tendency toward a poorly defined 

 porphyritic texture is manifested in some parts of the area. The 

 feldspars are partly of a pronounced pinkish hue, which impart a 

 slightly mixed pink and gray color to the rock. In some respects 

 hand specimens from the Raleigh and Greystone areas bear some 

 resemblance to each other; in others they are strikingly different. In 

 mineral composition they are essentially identical. 



The principal minerals are quartz, orthoclase, microcHne, micro- 

 perthite, a little acid plagioclase near oligoclase, biotite, apatite, 

 zircon, chlorite, muscovite, and kaohn. Microscopically the most 

 noteworthy feature of the granite in this area is the very small 

 amount of plagioclase present, which entirely fails in some of the thin 

 sections. When present, the plagioclase individuals show broad twin- 

 ning bands having extinction angles near that of oligoclase. Micro- 



