68 GEOLOGICAL SURVEY 
In the N. East corner of Lexington I saw some porphyritic sienite, that was taken from a well, 
which may be a continuation of the Montecello sienite, already mentioned. On the plantation of 
E. G. Palmer, Esq. a dyke occurs of great interest, from the light it throws on the origin of this 
rock. The dyke has embedded in it angular fragments of hornblende slate, of various sizes, 
evidently torn from the rock which it intersects, in its passage through it, in a molten state. The 
rock resembles a coarse breccia, and would be a beautiful ornamental building material: 
A sienitie vein occurs three or four miles from Smith’s Ford, Broad River, York District, which 
deserves notice, from the fact that it is intersected by veins of quartz, which have been worked for 
gold, to a depth of twenty feet. At Meansville, Union District, a sienitic granite occurs, upon which 
the slates of that region rest, as may be seen at the Fair Forest mines, as well as at those of 
Nuckols and Nott, near Pacolet, where the rock is intersected by auriferous veins. 
Eurite, which is a compound of quartz and feldspar, is found in many localities, forming con- 
spicuous veins. In the village of Edgefield one is found, which furnishes, by disintegration, a fine, 
white sand. And, near Abbeville Court House, Mr. Speirin pointed out to me a fine locality of por- 
celain clay, derived from this rock. North-west of the village I saw another vein, which contained 
garnets. 
The dykes of the State present many illustrations of the igneous origin of trap rocks. In the 
vicinity of some of the dykes of Edgefield, the clay slates are altered to porphyry. At Hale’s mine 
the slates are converted into a black scoria to the distance of four or five inches from the walls of 
the dyke. In Chesterfield the New Red sandstone is altered to a hard, black, compact rock, and 
portions of it resemble over-burned brick. 'The bituminous coal of the New Red in North Carolina, 
is converted into anthracite, wherever it is intersected by dykes. 
The dislocations and disturbances produced by the intrusion of the trap rocks, are rarely, in this 
State, sufficient to throw any obstructions in the path of the miner. The beds of magnetic iron 
ore, of York District, are sometimes dislocated by dykes, without producing any off-cast of impor 
tance. Many of the beds and veins in the gold-mines are intersected, and completely divided, 
by dykes, without producing any displacement, or in any other way affecting the productiveness of 
the mines. 
Mineral Contents.—The trap rocks of the southern portion of the Atlantic slope are singularly 
destitute of minerals of even scientific interest. Large quantities of magnetic iron ore, in the form 
of black sand, are washed out of the decomposing trap of Chester and Abbeville Districts. In 
Chester I found masses of compact magnetic ore, near Cornwell’s, that indicated a vein of consider- 
able size; but no further examination was made. The wacke which occurs at Durn’s, on Hard- 
labor Creek, near the Edgefield line, is easily dressed, and may be useful for a variety of purposes ; 
but I imagine that it will not stand the fire like soap-stone, which it resembles. 
