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40 HISTORY OF THE GEMS FOUND IN NORTH CAROLINA.
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the
search for gems irregularly, for periods varying in length, for several
years. Since 1885, however, but little has been done, owing to some
legal disputes as to the property.
The
largest emerald crystal found during this mining work was 8-1/2 inches
in length and weighed nearly 9 ounces (PL III, p. 8). It is now in the
Morgan-Bement collection at New York. This was one of nine crystals
contained in a single pocket, all excellent in color and partially
transparent, but somewhat flawed. One was 5 inches in length and others
were over 3 inches (PL III).
One
of the most noteworthy gems cut from the product of this mine was from
a crystal found in a pocket at a depth of over 43 feet. Its color is a
pleasing light green and it weighs 4 23/32 carats. In 1887, at a depth
of about 70 feet, another crystal was obtained that yielded a cut stone
of 5 carats. Both of these are too light in color to rank as fine gems.
The two largest, and a series of the smaller ones, went into the
cabinet of Clarence S. Bement, now the Bement-Morgan collection in the
American Museum of Natural History. Some fine ones are also in the
British Museum. The rich emerald color in many of these crystals is
confined to a border from 2/100 to 3/100 of an inch in thickness around
the edge and near the termination of the crystals. If this edge were
thicker, fine gems could be cut from it.
The
value of the emeralds in this deposit was relatively small compared
with that of the many slender crystals of hiddenite. Both these species
are in part silicates of alumina, but they differ in the other basic
element present, which, in hiddenite, is lithia, while in the emerald
it is glucina. Both gem stones owe their color to the same substance,
oxide of chromium. The emeralds found in this mine were very rarely
without flaws, while the hiddenite was notably free from such defects,
and varied in shade from a yellowish green to the deepest blue-green,
often oddly combining both extremes of color in the same crystal.
The
chemical composition of the emerald beryl is shown in the analysis
given below of a leek-green colored beryl from Alexander County:
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