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CORUNDUM GEMS.
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21
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exhibit
at the Columbian Exposition of 1893; these were subsequently unmounted
and displayed by the same firm at the Atlanta Exposition of 1895. They
now form part of the Tiffany-Lea collection, included in that of the
IT. S. National Museum at Washington. A number of others (see figures),
obtained at about the same time, are in the American Museum of Natural
History, New York. A fine series, both of crystals and cut gems, was
shown by the North Carolina Geological Survey at the recent Expositions
at Buffalo, 1901, Charleston, 1901-02, and St. Louis, 1904.
In
1896, the locality was visited and examined by Mr. C. Barrington Brown,
the eminent authority on ruby mining, who had previously prepared an
exhaustive report on the Burma region, in conjunction with Prof. J. W.
Judd, for the British Government.
In
1899, as above stated, Professor Judd and Mr. William E. Hidden
published a joint article, with crystallographic notes by Dr. J. H.
Pratt. This account embodied the results of Mr. Brown's visit, of Mr.
Hidden's operations on the ground, and of Dr. Pratt's studies on the
costal forms and their relations. It had now become clear that the
rubies from this locality occurred in a wholly different association
from any other corundum in the State, and the title of the article was
" On a New Mode of Occurrence of Ruby in North Carolina." The
surrounding rocks are schists and gneisses, often containing corundum,
but in elongated crystals and not of gem quality. Only a few miles away
are the dunite outcrops of the Culsagee and other localities, already
described. But at Cowee the rock is wholly different, and the forms of
the crystals also. The first accounts had reported a limestone as the
probable source of the valley deposit, and even as the matrix.of the
crystals, as is the case in Burma. But further study had disproved this
statement. Underneath the ruby-bearing gravel, comes a soft decayed
rock to which the name of saprolite has been given,—a result of the
decomposition of basic igneous rocks, in place. This is sometimes many
feet in thickness, but gradually passes downward into the unaltered
condition of the same rocks. Trial shafts show that this change begins
from a depth of some 35 feet, when portions of the unaltered rock begin
to be met with. The original rock, when reached, proves to consist of
several related varieties, comprising amphibolite, hornblende-eclogite
(garnet-amphibolite of some authors), and a basic hornblende-gneiss,
with some feldspars (labradorite and perhaps anor-thite). Some of these
rocks are doubtless the source of the rubies strewn through the
saprolitic material and the overlying gravel, though their actual
occurrence in the undecomposed rock has not yet been proved. The
crystals are distinct from any others found in North Carolina, but
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