392 THOMAS L. WATSON 



The component minerals are quartz, orthoclase, microcline, at 

 times microperthite, abundant plagioclase, a little biotite, magnetite, 

 chlorite, epidote, titanite, rutile, and occasional garnet. The granite 

 is largely a mixture of feldspar and quartz, with scant biotite as the 

 third principal component. One of the most striking features in the 

 mineral composition of the rock is its poverty in the ferromagnesian 

 mineral and the excessive plagioclase, which latter constituent exceeds 

 the potash feldspars in all the thin sections examined. Plagioclase 

 is in large, stout, rudely prismatic forms, polysynthetically twinned, 

 and corresponds in optical properties to albite and very acid oligo- 

 clase. Both orthoclase and microcline occur, the latter very variable 

 in quantity, being reduced to one or two grains in some sections and 

 in fairly good proportion in others. Microperthite is distributed in 

 small amount through some of the sections. Carlsbad twinning is 

 observed, but it is not so frequent as in some of the granites from other 

 localities in the state. In the pink phase of the rock the feldspars 

 are usually filled with closely crowded dust-like particles of a reddish- 

 brown color, which probably represent some form of iron oxide. 

 Biotite, when present in the thin sections, is of the usual kind, and is 

 distributed through the rock in small, very irregular shreds, altered 

 largely to chlorite. Quartz occupies well-defined areas between the 

 larger feldspars, forming an aggregate of interlocking fine grains, in 

 which feldspar may or may not appear. 



Crushing and recrystallization from the action of intense dynamic 

 forces are strongly emphasized in all of the thin sections. Finer 

 mosaics of quartz and feldspar border the larger individuals of the 

 two minerals and fill the interspaces. The larger laths of plagioclase 

 are fractured and broken, and in many instances curved and bent, 

 with irregular fractures and strained shadows common to the other 

 essential components. 



The Mooresville area. — The porphyritic granite of the Mooresville 

 area has been previously described on pp. 380 and 381. Attention is 

 here directed to the even-granular granite, which is a very fine 

 textured rock of dark gray color. It is strongly contrasted with that 

 of the Dunn's Mountain area described above. Orthoclase and 

 microcline are in nearly equal amount. Unlike the other areas, 

 plagioclase is very sparingly present, not more than a few grains 



