ON DHE OCCURRENCE OF APE LE GVEA ihn ID 
TOURMALINE BUNCHES IN THE STONE MOUNE 
TAIN GRANITE OE GEORGIA: 
Aplite and pegmatite.—Careful field study of the larger and 
principal granite areas in Georgia, by the writer, indicates the 
general absence of true aplites therefrom. They have been 
observed in association with the granite masses only at one 
locality in the state.. Since the border portions of the granite 
masses are usually covered with a considerable depth of residual 
decay and are seldom exposed, it is not possible to say whether 
aplites as border phenomena exist, as described by Kemp,* in 
some of the southern Rhode Island and Connecticut granites. 
Several aplite dikes less than six inches in width are exposed 
in the quarries opened on the northwest side of the huge doming 
ridge known as Stone Mountain, sixteen miles east of Atlanta 
(Plate VI1). Pegmatites are common associates in the Stone 
Mountain granite and also in the other larger granite masses 
examined in the state. They consist chiefly of coarse inter- 
crystallizations of potash (orthoclase and microcline) and soda 
(albite) feldspars with quartz, subordinate amounts of both 
biotite and muscovite, and occasionally red garnet and tourma- 
line. So far as my observation goes, the feldspars in the peg- 
matite greatly exceed in amount the quartz. The granitic 
pegmatites are sometimes replaced, however, by those of prac- 
tically pure quartz. In the Stone Mountain pegmatites the dark 
minerals, mica, tourmaline, and garnet, are frequently concen- 
trated along the central axis of the dike or vein, rather than 
distributed through the light-colored quartz-feldspar portions. 
Where observed the granitic pegmatites are monotonously alike, 
and present no unusual features. 
The principal aplite in the Stone Mountain granite is banded 
with pegmatite, the aplite forming the border next the granite 
t Bulletin Geol. Soc. Amer., 1899, Vol. X, p. 372. 
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