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THE BOOK OF DIAMONDS
through
a diamond, a constant, correctly shaped spray of oil is delivered and
the efficiency of the nozzle is not impaired by the action of grit or
acid in the oil, or by the great heat.
Boring
the hole in a diamond for a die or a nozzle is an interesting process.
A needle, impregnated with diamond dust, hammers away on the stone for
about a week before the hole is bored. This drilling operation costs
seven times as much as the diamond itself.
About
forty-five per cent of the product of African diamond mines consist of
bort, an opaque dark colored variety of diamond, called also black
diamond. Such crystals weighing from one-half to one carat each are
used extensively as teeth in stone-saws for sawing marble and stone for
building purposes.
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