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80 PRECIOUS STONES
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CHAPTER XIII.
VARIOUS PRECIOUS STONES.
The Diamond.
To
recapitulate certain of the facts respecting the diamond.—This
wonderful gem has the distinction amongst precious stones of being
unique ; though many are composed of two, three, or but a small number
of elements, the diamond is the only stone known consisting of one
element, and absolutely nothing else—pure crystallised carbon. Its
hardness is proverbial ; not only is it nn-touched by the action of a
hard file, but it occasionally refuses to split when struck with finely
tempered steel, which it often causes to break. Such was the ease with
the South African diamond, for when the knife that was to break it was
struck smartly with a steel bar, the first blow broke the blade without
affecting the diamond, yet a piece of bort, or diamond dust, splinters,
or defective diamonds (all these being called bort), may readily be
pulverised in a hard steel mortar with a hard steel pestle. The diamond
is the hardest stone known : it is also the only stone known which is
really combustible. It is of true adamantine lustre, classed by experts
as midway between the truly metallic and the purely resinous. In
refractive power and dispersion of the coloured rays of
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