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PRECIOUS STONES.
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It
is used to provide a cutting edge for lathe tools intended for the
working of very hard steel, and Max Bauer instances its use in tools
for boring cannon at Krupp's works at Essen.
Of
its more frequent use for personal adornment little more need be said.
From the time it was first known Diamond has held its place with a
uniformity more marked than any other precious stone. An exception is
given by King, who states that the Persians only allowed it to rank
after Pearl, Euby, Emerald, and Chrysolite.
In
the earliest times the gem seems to have been used largely as a spell
against plagues, and the more alarming manifestations of Nature's
activity; in mediaeval times, chiefly as signs of magnificence and
wealth. Thus the robes and crowns of kings were adorned with them, and
it was not till the middle of the fifteenth century that it became much
in vogue for personal adornment by women, at which time it was
introduced by the ladies of the French court.
Diamond
as a rule requires little preparation before cutting begins. Should the
stone show surface films these are usually easily removed by treatment
with " aqua-regia " (a mixture of hydrochloric and nitric acids). Any
imperfections are removed as far as possible by cleaving, and the
stone at the same time brought to the octahedral form, ready for
grinding, if it is to be cut as a brilliant. By far the greatest number
of stones are cut after this pattern now. So much has Diamond come to
be associated with the brilliant cut that the term " brilliant" is
often erroneously used as synonymous with Diamond. Even very small
stones can be cut as brilliants by the Dutch
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