20 CORUNDUM IN THE UNITED STATES. [bull. 180. 
These are often wrapped with chlorite. Nodules of a black-green 
hornblende and an emerald-green actinolite are also found in the 
biotite. There has been no great quantity of the corundum found. 
This zone of biotite is probably the result of contact metamorphism 
of the saxonite on the gneiss, and the inclosing corundum was formed 
at the same time. This is similar to the large quantity^ of corundum 
occurring in biotite at the contact of saxonite and gneiss at the Bad 
Creek mine, Sapphire, N. C. (See page 62.) 
CORUNDUM IN ENSTATITE. 
Enstatite is rather common as a secondary product at many places 
where the corundum occurs in peridotite, and is thus an associate of 
corundum at these localities. Occurrences are rare, however, of 
corundum in an enstatite that is the original rock. Where thus found 
the rock is made up chiefly of the orthorhombic pyroxene, enstatite, 
in bladed interlocking crystals of a grayish color. It is always more 
or less decomposed into talc. 
At the Rattlesnake mine, Sapphire, Jackson County, N. C, and on 
the West Fork of the French Broad River, in Transylvania County, 
N. C, corundum has been found sparingly in the borders of an ensta- 
tite rock. 
Enstatite rocks are somewhat common in North Carolina, but acces- 
sory minerals in them are rare, and the most common one observed is 
chromite, in small grains. 
CORUNDUM IN SERPENTINE. 
At a number of peridotite localities in North Carolina and Georgia 
crystals and fragments of corundum have been found that were sur- 
rounded by serpentine, but nowhere in this southern section of the 
peridotite belt has corundum been found associated with the larger 
masses of serpentine. In Chester and Delaware counties, Pa., 1 there 
is a long belt of serpentine rocks, part of which, at least, have been 
derived from peridotite rocks, and in connection with these, in the 
eastern part of Chester County and the western part of Delaware 
County, corundum has been found. In this, as in the peridotite, the 
corundum occurs near the contact of the country rock. Considerable 
plagioclase feldspar is associated with the corundum in the vein in a 
manner somewhat similar to the occurrence of this mineral at the 
Cullakeenee mine, Buck Creek, Clay County, N. C. In the South 
corundum has not been found as constantly associated with the ser- 
pentines as it is with the peridotites, but chromite is found very 
abundantly with many of them. 
Cutting through the serpentines on the eastern slope of Spanish 
Peak, Plumas County, Cal., are white, coarse-grained dikes composed 
of corundum and oliiroclase. 
1 Geol. Survey Pennsylvania, C 4 , 1883, p. 351. 
