62 GEOLOGICAL SURVEY 
the sandy Tertiary beds, yet wherever it appears it is found in the relative position just mentioned, 
showing clearly its agency in raising the overlying rocks to their present inclined position. 
Graniteville, on Horse Creek, is the most southern locality of granite in the State. The rock is 
laid bare on the banks and in the bed of the stream, by the removal of the sand and clay by 
which it is covered up to the right and left. It is a hard, compact, bluish rock, composed of quartz 
and feldspar, with very little mica—the feldspar generally predominating. On the right bank of 
the creek it is much disintegrated ; the feldspar is white, and in a state of decomposition, and even 
where the rock is solid, it seems to have lost its peculiar lustre. 
A little higher up, and on the opposite bank of the stream, a quarry has been opened, where the 
rock presents its normal character. It is intersected with veins of feldspar, and the surface broken 
up into prisms by jointed structure. The direction of the principal joints is about N. 25° W. It 
is also separated into lamine, two or three feet in thickness, parallel with the surface. Near the 
dam a similar structure prevails, but where the rock is disposed to disintegration, the iron of the 
decomposing feldspar, which is set free, forms, by segregation, yellow bands, parallel, not with the 
horizon, but with the surface of the rock, giving it a curious striped appearance ; sometimes these 
bands or stripes are much curved, yet they preserve their parallelism. 
Along the banks of the stream, for a distance of four miles, to the head of the pond at Vaucluse, 
this rock is exposed, and near the Factory it presents a fine locality for the examination of the pris- 
matic structure, which results from the intersection of joint lines. 
The following diagram represents the relative position of the granite and overlying rocks between 
Horse Creek and Edgefield. 
i at mM m ur 
SOR ey om 
ee nies 
= iiss rnin 
1.—Granite. 2.—Clay slate. 3.—Tertiary beds. 
On Cloud’s Creek is a locality of Porphyritic granite, with white feldspar and black mica, noted 
for the mill-stones it furnishes for the neighboring Districts. It occurs in round weathered masses, 
but little elevated above the surface. ’ 
A coarse, crystalline granite occurs on a small stream West of S. Edisto, where the Columbia 
road crosses it; it is overlaid by gneiss and hornblende slate. Thick beds of gneiss, having but 
little mica, and which are consequently but slightly fissile, cross the river. 
On Lightwood Creek, at Gen. Quattlebum’s mill, granite comes to the surface, and in the mill- 
race it is covered by a series of talcose and mica slates, together with beds of feldspathic rock. On 
the margin of the pond masses of rough, porous quartz rock, presenting almost a vesicular structure, 
is strewed over the surface. On examination this rock seems to be the result of the decomposition 
and consequent disappearance of crystals of feldspar which were disseminated through the quartz. 
Could it be found in sufficient quantity, it would make a good substitute for burr-millstone, which 
it somewhat resembles. 
