CORUNDUM IN METAMOEPIIIC ROCKS. 57 
CORUNDUM IN AMPHIBOLE-SCHIST. 
At the Sheffield mine, in Cowee ToAvnship, Macon County, N. C, 
corundum has been mined in a saprolitic rock at various times for a 
number of years. In a shaft sunk to determine the depth of the 
corundum-bearing saprolite, solid, 'unakered rock was encountered. 
The shaft, which was 87 feet deep, passed throuo-h the following 
rocks: The first 12 feet (a) was through the saprolite, in which thei-e 
wei-e seams of kaolin; the next 2 feet (h) were corundum bearing. 
I^'rom l-t to 28 feet (c) the same saprolite was encountered; the next 2 
feet {(I) were corundum bearing, followed by 10 feet {e, from 30 to 40 
feet) of the saprolite, and 2 more feet (/) that were corundum bear- 
ing. From 42 to ()3 feet (g) the rock began to be less de(;om posed, 
and from G3 to (U; feet (h) another seam of corundum-bearing rocJc 
was encountered. From this point to the bottom of the shaft the 
rock became more and more solid, until at 77 feet (/) the fresh rock 
"was encountered. These various seams in the rock are very pro- 
nounced. They dip 30° toward 4he west near the top, but become 
nearly horizontal near the bottom of the shaft. The seams of decom- 
posed feldspar observed in a become less and less kaolinized, until in i 
the seams are of pure plagioclase feldspar. In / there are two seams 
of corundum similar to h, d, and /, although in the fresh rock the 
corundum seams are not as pronounced as in the saprolitic rock. 
There is often a considerable amount of feldspar bordering the seams 
of the corundum. The general trend of the rock is about N. 5° to 
10° E. 
From what could be seen of the solid and the saprolitic rocks, it is 
evident that the corundum occurs at intervals in the rock in seams a 
lew feet in width. The corundum may comprise 10 per cent or more 
of the veins, but the quantity in the rock that it would be necessary 
to mine woidd probably not be over a few per cent. The actual 
width of the dike is not known, but the saprolitic rock has been cut 
across for about 100 feet in a direction nearly at right angles to its 
strike. 
The fresh rock at the bottom of the shaft is somewhat varied in 
appearance, and though it does not show any definite gneissoid struc- 
ture, it sometimes closely resembles it. There are streaks in the rock 
a few inches thick, the more finely divided portions of which are dis- 
tinctly gneissoid. 
Some portions of the rock are decidedly porphyritic, and contain 
phenocrysts of a light-gra}^ amphibole, a centimeter in diameter, in a 
groundmass of feldspar. A large part of the rock is made up, how- 
cxer, of small, roughly outlined prismatic crystals of an amphibole, 
