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PRECIOUS STONES
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by
some mineral for which it had an affinity, became, by natural
processes of heat, pressure, and cooling, solidified and crystallized.
Whatever
the processes of nature were, the attempts to make them artificially
have shown that the forces and time necessary are beyond our compass.
Science and present means at its disposal have succeeded only in making
a few very minute and imperfectly crystallized particles, sufficient to
illustrate vaguely the larger method of nature.
The
qualities which make the diamond valuable are its extreme hardness,
great lustre, and the reflective, refractive, and dispersive powers
which it possesses.
It
is the hardest substance known, and for purposes of comparison is rated
10 in a scale running from 10 to I. On account of this excessive
hardness, the ancients could only partially polish it, and did so by
rubbing one rough diamond against another,—" bruting," as it was
termed. This knowledge of its extraordinary hardness gave rise to an
error which exists to some extent even now. It was said that it was so
hard, one could be laid upon an anvil and struck with a hammer without
danger to the stone. Many beautiful gems have been destroyed by this
test, for though they are so hard that they will wear a way through any
other substance, they are also brittle, easily fractured, and, by
pounding in a steel mortar, may be reduced to powder. They may be also
worn away by constant rubbing against softer material. As rocks are
worn away by the constant washing of water, so would friction with
other substances, if persisted in, eventually wear even upon a diamond.
In fact, Mawe says, " I am in possession of a globular diamond, upon
the surface of which neither the naked eye nor the microscope is able
to discover the smallest appearance of facets." He mentions this to
refute the statement that diamonds were never found as rolled pieces.
The degree of hardness varies in different crystals, and
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