Piedmont Plateau of Geor gia.-^W atson. 207 
regular oval-shaped area of quartz and feldspar, from which 
the two micas, muscovite and biotite, have been excluded. As 
a rule, the white areas containing- the tourmaline bunches are 
only a fraction of one inch to several inches in diameter, though 
larger ones are by no means exceptional. Small crystals of 
red garnet are not uncommon. The joint planes exposed in 
several quarries on the north side of the ridge are coated with 
a sulphur-yellow incrustation, which, upon chemical investiga- 
tion, proved to be a mixture of uranophane and hyalite, with 
the former in excess. 
Approximately 12 miles southwest from Stone mountain 
in the same county, is a second exposure of a biotite-bear- 
ing muscovite granite, light gray in color and finely crystalline 
in texture. The rock has been used to some extent as a mon- 
umental stone. It consists of the same materials in the same 
proportions as the Stone mountain granite. Micropegmatitic 
intergrowths of quartz and feldspar are common. The pris- 
matic inclusions of apatite in the quartz are frequently bent and 
broken, and, in some cases, the parts have slipped past each 
other. 
Some effects of strain are frequent in all the above types 
of granite, indicating that they have suffered from partial 
dynamic metamorphism. The microscopic evidence strength- 
ening this conclusion is undulatory extinction in the quartz : 
fracture lines crossing the quartz and sometimes the larger 
feldspar anhedra ; and somewhat increased microcline in 
places, manifesting some evidence of a strained condition. In 
Meriwether county, and several of the nearby counties, areas 
of rather pronounced foliated granites of the same mineral and 
chemical composition, resembling in other respects the massive 
phases, are found. The gradation, if such exists, between the 
massive and foliated granites could not be satisfactorily traced 
in the field, in this area, but the laboratory evidence strongly 
favors such. If this be true, the traceable gradations in the 
field are rendered impossible on account of few exposures and 
the very heavy covering of residual decay. In thin sections of 
the foliated rocks, the evidence of pressure metamorphism is 
increased in some peripheral shattering of the larger quartz 
and feldspar individuals. Pressure metamorphism is further 
made evident in the Stone mountain type in a slight pseudo- 
foliation. 
