28 
OF GNEISS. 
posed that there is at least an approach to parallelism amongst 
its laminae. In general also, instead of being dispersed through 
the whole body of the rock, it is separated from the other ingre¬ 
dients into plates or seams, by which the granular compound of 
quartz and feldspar is divided into tables of greater or less thick¬ 
ness, so that if a small piece of gneiss be examined, it will appear 
to be granular and massive, if a large mass be subjected to obser¬ 
vation, it will as evidently be stratified and slaty. 
For mica, there is often substituted in the composition of gneiss, 
hornblende, and sometimes, though rarely, talg, chlorite, or argil¬ 
lite. The variety containing hornblende is found abundantly 
amongst the mountains in the western part of North Carolina. 
Besides the varieties produced by the substitution of these sub¬ 
stances for the mica, there are many others created by the dis¬ 
appearance, or by some modification of the arrangement of the 
quartz and feldspar, so that the rock passes into granite on the 
one hand, and into the formations to be immediately noticed, 
mica slate and quartz rock, on the other. Like granite, it is 
rendered porphyritic by the superaddition of large crystals of 
feldspar, and takes the name of porphyritic gneiss. Fine exam¬ 
ples of this may be seen at Graham’s furnace and in other parts of 
Lincoln county, and in the ascent of the Blue-Ridge, by the way 
of the Hickory-nut gap, in Rutherford county. The court-house 
in Burke, is built of this variety. 
That variety of gneiss which abounds in mica, has less firmness 
and solidity than granite, it is less beautiful, but being divided by 
the seams of mica into tables, it is quarried with greater ease, and 
if it be of a kind that will stand the weather, in which particular, 
gneiss is generally superior to granite, it is in request as a buil¬ 
ding stone, and for other economical purposes. A quarry of the 
hornblende variety has been explored for many years, at Durham, 
in the state of Connecticut. It is raised in tables, varying from 
an inch to two or three inches in thickness, and shipped to the 
large cities along the coast, where, on account of the evenness of 
its surface, it is much esteemed as a flagging stone. Gneiss is 
one of the most widely distributed of the rocks. In North Caro¬ 
lina it is found along the Cape Fear in the upper part of Cum¬ 
berland, and in the western counties. 
The crystalline mineral forms, which are sought after with so 
much eagerness by collectors, and esteemed the most valuable 
ornaments of our mineralogical cabinets, are not as numerous and 
abundant in gneiss as in granite; but it often embraces extensive 
formations of other rocks, as limestone, porphyry, compact- 
feldspar, and quartz, and it is rich in the metallic ores. Most of 
the metals occur in it, sometimes in beds, but more frequently in 
veins. IMany of the mines of Germany and Sweden are in 
gneiss. The most valuable beds of iron ore, in the western part 
of North Carolina, are in a region where gneiss abounds, but the 
ore is frequently in immediate contact with some other rock. 
