744 THOMAS LEONARD WATSON 
Airy, North Carolina, granite, 52.71 per cent. The ratio of potash 
to soda-lime feldspar in the York County granite is 1:2.6; Mount 
Airy granite, 1:3.6. 
York County “Mount Airy 
South Carolina North Carolina 
SIO Baty tear 68.90 70.70 
Bae Ea ayem ay tocsteaele 15-75 16.50 
CHOM sae he rice ooo os 1.1 
He Ol aeracticcs tase I.49 Sia 
INN) Weal © Jesper le ca ee Tae 0.74 0.29 
CaO erie ata siden 2.66 2.96 
Na,O ren ipertom aie: 4.76 4.50 
ISA OUS Geo plot en SpmG 3-49 2.45 
The Columbia red-gray granite.—The coarse crystalline red- 
gray granite quarried at the Smith Branch (County) Quarry, two 
miles northwest of Columbia, is taken as the type. It does not 
differ essentially in mineralogy from the gray types described above, 
although it bears no resemblance to them or to any granites in the 
other southern states, in the hand specimens. The granite of the 
Casparis Quarry near Lexington and to the north of Batesburg in 
Saluda County, S. C., differs from this type only in finer crystallization. 
In each of these localities the feldspar has pronounced red color, 
which gives to the granite its characteristic shade. More or less 
tendency toward porphyritic texture is exhibited in this type of 
granite. Orthoclase, microcline, oligoclase, quartz, biotite, apatite, 
magnetite, and the usual secondary minerals are present. ‘Twinning 
on the Carlsbad law is noted in the potash feldspar. A chemical 
analysis of this type has not been made as yet, but the thin sections 
indicate the usual richness in soda-lime feldspar. 
PORPHYRITIC GRANITES 
Porphyritic granites are common over many parts of the crystalline 
area in South Carolina, but extensive continuous areas in which 
porphyritic texture is developed are apparently less frequent than 
in Georgia and North Carolina. Though porphyritic texture is 
quite freely developed in many of the granite areas, it either grades 
within rather short intervals into the more dominant even-granular 
texture or else is not of so pronounced a type. Like the even-granu- 
