Scientific American Supplement No. 822, October 3, 1891Various
Science
Scientific American Supplement No. 822, October 3, 1891
Various
Science -- Periodicals
The colors of the beryls grade from an almost colorless mineral
(goshenite) though faintly green, with blue reflections, yellowish
green of a peculiar oily liquidity (davidsonite), to honey yellows
which form the so-called "golden beryls" of the trade, and which have
a considerable value. These stones have a hardness of 8, and when cut
display much brilliancy. Many assume the true aquamarine tints, and
others seem to be almost identical with the "Diamond of the Rhine,"
which as early as the end of the fifteenth century was used as a
"fraudulent substitute for the true diamond" (King). Few, very few,
belong to the blue grades, and the best of these cannot compare with
those from Royalston, Mass. Those of amber and honey shades are
beautiful objects, and under artificial light have a fascination far
exceeding the olivine or chrysoberyl. These are not as frequent as the
paler varieties, but when found excite the admiration of visitor and
expert. It seems hardly probable that any true emeralds will be
uncovered and the yellow beryls may not increase in number. Their use
in the arts will be improved by combining them with other stones and
by preparing the larger specimens for single stone rings.
Very effective combinations of the aquamarine and blue species with
the yellow may be recommended. Tourmaline appears in some quantity,
forming almost a schist at some points, but no specimens of any value
have been extracted, the color being uniformly black. The garnets are
large trapezohedral-faced crystals of an intense color, but penetrated
with rifts and flaws. Many, no doubt, will afford serviceable gem
material, but their resources have not yet been tested by the
lapidary.
While granite considered as a building stone presents a complex of
quartz, mica, and feldspar so confusedly intercrystallized as to make
a homogeneous composite, in the present mass, like the larger and
similar developments in North Carolina, these elements have excluded
each other in their crystallization, and are found as three separate
groups only sparingly intermingled. The proportions of the constituent
minerals which form granite, according to Prof. Phillips, are twenty
parts of potash feldspar (orthoclase), five parts of quartz, and two
parts of potash mica (muscovite), and a survey of Mr. Wilson's quarry
exhibits these approximate relations with surprising force.
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