16 HISTORY OF THE GEMS FOUND IN NORTH CAROLINA.
known
as villarsite. Dr. Raymond fully perceived its character as an igneous
intrusion, differing from some other writers on this point, since
clearly established. Dr. Chatard describes the Culsagee outcrop as
consisting of chrysolite (dunite) mingled with hornblende. The
corundum is enclosed among various hydromicaceous minerals, commonly
grouped under the term chlorite, between the gneiss and the dunite,
from the alteration of which they have evidently been formed. It occurs
chiefly in crystalline masses, often of considerable size, and
sometimes suitable for gems (PL IV, A). At other parts of the mine it
is found in small crystals and grains mingled with scales of chlorite,
forming what is called the " sand vein." This is so loose and
incoherent that it is worked by the hydraulic process; and the small
size of such corundum is the saving of much labor in the next process
of pulverizing. At Buck Creek the chrysolite rocks cover an area of
over 300 acres, and from that point southward the hornblende rocks
assume greater proportions, being associated with albite instead of
the ordinary feldspar and forming an albitic cyanite rock. There is
also found here the beautiful green smaragdite, called by Professor
Shepard chrome-arfvedsonite, which, with red or pink corundum,
forms a beautiful and peculiar rock curiously resembling the eclogite
or omphacite rock of Hof, in Bavaria, as Professor Shepard had noted in
his early article in 1872.
Both
these localities have also been recently described, with maps, in the
admirable report of Dr. J. H. Pratt and Prof. J. V. Lewis, elsewhere
referred to.16
The
resemblance in the occurrence of the North Carolina corundum to that of
Mramorsk in the Ural Mountains, as described by Prof. Gustav Rose of
the University of Berlin, has been shown by Professor Genth." There the
associated species are serpentine and chlorite schist, sometimes with
emery, diaspore, and zoisite, very similar to the chrome serpentine
corundum belt of the Southern States. The emery deposits of Asia Minor
and the Grecian Archipelago, according to Dr. J. Lawrence Smith," yield
that substance in marble or limestone, overlying gneissic rocks; while
with it are associated many of the same hydromicaceous and chloritic
species that accompany both the New England emery and the southern
corundum.
With
more particular reference now to the actual gems yielded at these
various localities, we may note that they occur in two distinct forms:
first, as crystals, of which the usual forms for sapphire are doubly
termi-
