CORUNDUM IN IGNEOUS ROCKS. 38 
rock. This zone is divided — in one ])liU'e almost pinched oiil — by a 
mass of serpentine. 
It is to be noted that the zones 1, 2, 8, 4, 5, and (>, of fig. 7, are 
practically identical, respectively, with the zones /•, /, //, ^/, /, and e of 
fig. 6. This marked similarity is noted further on page 85, under 
the discussion of the origin of corundum in tlu* ])eridotites. 
An important variation from the normal modes of occurrence with 
pcridotite, as just described, has been observed at a number of locali- 
ties by the develoj^ment of a zone of corundnmdnniring plagioclase. 
This is found either in the corundum-bearing zone of chlorites and 
vermiculites {e and (> of cross sections given in figs. G and 7), or 
entirely replacing these zones. The feldspar, in the specimens deter- 
mined, is a basic lime-soda species; is sometimes fine grained and com- 
])act; at other times it is very coarsely crystallized, and varies in dif- 
ferent localities from a fcAV inches to several feet in thickness. In 
addition to the corundum, it is found to 
contain, in different localities, large masses 
of zoisite, coarse black hornblende, and 
other minerals. Examples of these zones 
of feldspar and corundum are found at a 
number of places on Shooting and Buck 
creeks, Clay County ; at the Bad Creek 
mine, Sapphire, Trans^dvania County, and 
at the Carter mine, Madison County, N. C. ; 
{;nd also at the Track Kock and Laurel 
simi- 
lar interior vein at the Hamlin mine, on Egypt mine, Yancey county, 
the headwaters of Ellijay Creek, m Macon ^' ^' 
County, N. C., contains, as its central member, a band of pegmatite 4 
inches thick, but not bearing corundum, so far as observed. This 
occurrence is very similar to the occurrence of corundum in plumasite 
described on page 42. 
At all of the corundum localities examined a careful search has been 
made to find corundum directly surrounded by the peridotite, but this 
has been observed at only one locality — the Egypt mine, on the west- 
ern slope of Sampson Mountain, in Yancey County, N. C. The 
few specimens obtained w^ere collected by Mr. U. S. Hayes, who 
developed the corundum property in that section. One specimen 
shows a prismatic crystal of the corundum surrounded by a granular 
peridotite (dunite), but with none of the chlorite minerals which 
usually intervene. The dunite is not quite fresh, but is stained a yel- 
lowish brown by iron oxide and is rather friable. On the basal sur- 
faces of the corundujn a little muscovite is developed. This has been 
observed on corundum from other localities. 
Bull. 269—06 M 3 
Ci • T> 1 r^ i- (^ i • • Fig. 8. — Corundum crvstal in- 
reek mines, Rabun County, (xa. A simi- ^,^^^^ ,^^ ^.^.^,^^^j^^/ ^^,^.^^^ 
