78 GEOLOGICAL SURVEY 
The sharp, irregular and notched outline of the crest of this mountain, when seen from the battle- 
ground, and which contrasts so strikingly with the softened and undulating contour of the other 
mountains of the blue ridge, is due to the indestructible nature of this rock, which has preserved its 
angles and fractured surface as sharp as if it had but yesterday been torn and upraised from its 
original horizontal bed. f 
Following the ridge into this State, we find the rock passing into mica slate, but re-appearing : 
again near Broad River. At the head of one of the islands, opposite the iron-works, it may be 
seen in large rhomboidal masses, which have fallen down, and lie scattered, in confusion, on the 
surface. On the right bank of the river it rises gradually till it reaches the top of Gelkey’s moun- 
tain, where it appears as if piled up above the slates, which lie on each side of the mountain. ‘To 
the north of this other spurs are found capped with this rock, which also present, on their surface, 
the appearance of a conglomerate. Towards the South-west it subsides with the surface of the 
country, and re-appears in the talcose slates, on the edge of Union and Spartanburg. It is here 
quite arenaceous, having barely sufficient coherency to form blocks for the hearthstones at the 
furnaces—a use for which it is highly prized. Henry’s Knob, an isolated little mountain in York 
District, presents a fine example of this rock, which protrudes in a thick stratum from between the 
mica slates. Ruff’s Mountain, in Lexington, affords another good locality. Both here and at 
Henry’s Knob the surface of the rock is occasionally studded with crystals of kyanite. 
The arenaceous quartz, so common in the auriferous rocks of Chesterfield and Lancaster, may 
be referred to a variety of this rock; but at a certain distance below the surface, beyond the jafn- 
ence of atmospheric agencies, it becomes a true hornstone. 
Another remarkable form presented by this rock, is the itacolumite, or flexible quartz, which is 
found in one or two localities in the State. The most remarkable of these occurs very near the 
Limestone Springs, about a hundred yards north of the point where the road to Cherokee Ford 
erosses the Union road. The rock is seen on the way side and extending into the woods, in the 
direction of the Springs, and can at once be recognized by its smooth and striated surface. On 
examination portions of the rock will be found to split readily into flexible lamin, varying from 
one-eighth to an inch in thickness ; the surface of the lamin being covered with thin plates of 
mica. It passes even in the same mass into compact quartz, to be distinguished from common 
quartz only by its stratified structure. 
The flexible portions of the rock seem to be in the incipient stages of disintegration, evidently 
produced by the oxidation of the iron, This rock, in its compact form, is seen surmounting the 
limestone at the Springs. 
The other locality is in Pickens District, between West Union and Oconee Mountain, on the land 
of Dr. McElroy: It is not very prominent, but may be observed crossing the road, and on a small 
branch near the house. 
Prof. Shepard has recently directed attention to this rock, on account of its connection with the 
diamond-bearing rocks of Brazil and the Kast. 
In South Carolina quartz rock is certainly associated with the most interesting group of rocks in 
the State, as will appear from the following section. 
