68 
Journal of the Mitchell Society 
[November 
green to black color, composed chiefly of olivine and a lime 
feldspar and is rather abundant in some seetions and occurs in 
dikes from a few to over a 100 feet wide. The outcrop is gener- 
ally marked by abundant characteristic spheroidal “nigger-head” 
bowlders. The diabase dikes cut the rocks at various angles, 
though in many cases they have a north to northwest strike. 
Structure 
The rocks of this region have undergone extreme regional meta- 
morphism, with accompanying folding and faulting. The mash- 
ing and recrystallization of the rocks of the Carolina gneiss forma- 
tion have been so extensive, in some cases, that much of the 
original sedimentary structure and igneous texture have been 
destroyed. The folding of the older formations has resulted, in 
some places, in complex structure of both large and small dimen- 
sions. Some of the folds extend over miles of region, while others 
are confined to a few feet or inches. The minor deformations and 
crumplings — miniature Appalachian folds — seen in some rock 
exposures portray the form of the larger folds. The Carolina 
gneiss has been intruded by rocks of later age and cut by them 
into irregular-shaped masses, many of which fork out into long 
tongues or occur as narrow streaks in the intrusives or vice versa. 
There have been successive intrusions of igneous rocks of later age 
into the earlier formations. Thus the Carolina gneiss is cut by 
the Roan gneiss, and both are cut by granites of later age. 
The structure of the pegmatite in this region is quite variable. 
In some places the pegmatite occurs in sheets or lenses interbedded 
and folded with the inclosing gneisses and schists. In other places 
it occurs in dikes, veins, or lenses either conformable with the 
inclosing rocks through part of its extent and cutting across them 
in other parts, or in irregular masses having no definite orienta- 
tion in the surrounding formations. In pegmatized rock masses 
pegmatization has generally affected certain beds, which grade into 
regular pegmatite in either the direction of their greatest or that of 
their least extension. In such rocks it is often impossible to de- 
termine the line of demarcation between the two. There is also 
a gradation between the pegmatized beds and ordinary gneiss. 
