130 
GEOLOGY OF NORTH CAROLINA. 
It weathers into rough, jagged, honey-combed, and laminated or slaty- 
looking ridges, and decomposes into a dark, gravelly, barren soil, of the 
following composition ; (sample from Hampton’s, in Yancey county) : 
Silica, (8. OS sol.). 
Oxide of iron,. . . 
Alumina, 
Lime, 
Magnesia, 
Sulphuric acid,. 
Chlorine, 
Phosphoric acid, 
Organic matter, . 
Water, 
G3.15 
S.53 
3.41 
0.22 
2.3S 
0.10 
0.02 
0.18 
17.00 
4.50 
99.49 
n which the absence of potassa and soda is notable, and the abundance 
of iron, and of organic matter especially, the latter no doubt exceptional 
and accidental. The most common and characteristic minerals of the 
North Carolina dunyte are chlorite, talc, asbestos, chalcedony and chro- 
mite, the last in scattered grains and in coarsely granular irregular veins, 
or pockets. In many places several other species are quite common, for 
example, bronzite, nodular masses of enstatite, a bright, green, granular, 
hornblendic mineral, which Genth makes kokseharoffite, serpentine, and 
a curious cup foliated variety of talc, &c. One of the most interesting 
and valuable minerals, and one which is also of common occurrence, is 
corundum, which occurs in tabular, cleaveable masses and in crystals. 
For a particular account of this and the other associated minerals, the 
reader is referred to Dr. Genth’s and Mr. Smith’s papers in the Appendix, 
and to Dr. G.’s special paper on corundum, constituting No. 1 of “Con- 
tributions from the Laboratory of the University of Pennsylvania,” and 
to Prof. Shephard, in the American Journal of Science, August, 1872. 
Crystalline limestone occurs in three or four small ledges (beds), of a 
foot or two in width to a rod or more, in one small tract on the French 
Broad, in and a few miles below Marshall, in Madison county. It is as- 
sociated, at one of these outcrops, with a greenish hornblendic rock, and 
is filled with minute, rounded grains of green coccolite. There are also 
occasional dikes of serpentine and of pyroxenyte; one of each maybe 
seen along the Swannanoa road in Buncombe. And the hornblende 
slates are sometimes epido.tic, as in Mitchell near Flat flock* The rocks 
