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Diamond
Cutting
Diamonds could not be cut at all if not for the fact
that the hardness of diamond is not uniform. The point
of an octahedron, for example, is harder than the surface
of an octahedral face. Thus; powdered diamond can cut
into a diamond crystal and abrade its surface because
the powder will always contain some particles oriented
in a "hard" direction.
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Early
diamond jewels were primarily talismans, so the stones
did not have to be polished and rough crystals were
used. The art of diamond cutting originated in Venice
in the early part of the 14th Century and spread to
Paris and Antwerp. Today, London is the trade center
for rough diamonds. |
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From
here they are sent to Antwerp, Bombay, Tel Aviv, Johannesburg,
New York, San Juan, Amsterdam, and other cities for cutting.
Russian-made diamonds are also appearing on the market in
steadily growing numbers.
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DIAMONDS,
GEMSTONES & CRYSTALS
FACTS & FIGURES |
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are several steps in diamond cutting. The first
gives initial shape to the stone, and is known
as cleaving. Diamond readily splits in directions
parallel to the octahedral faces, and cleaving
rapidly removes unwanted material or separates
rough into portions which are sepa¬rately
fashioned.
An alternative to cleaving is sawing, a step that
is also useful in removing flawed areas from a
diamond. A modern diamond saw is a small disc
of phosphor-bronze whose edge is impregnated with
diamond powder. In times past, sawing was done
with a length of fine wire, a tremendously laborious
and time-consuming job. It is reported that it
took almost a year to saw the 410-carat Regent
Diamond in half. Today the operation would require
only a few days.
The
next step, called bruting, consists of rounding
the corners of the octahedron. This was originally
done by hand with a diamond tool called a sharp,
and is done today by machine. The modern equivalent
of bruting is called rounding up. Small flaws
can also be removed in the rounding-up process,
and weight loss kept to a minimum. |
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Occasionally
a small portion of the original diamond crystal surface is
left on the girdle of the stone. This area, called a natural,
indicates that little material was wasted in cutting, although
its presence is not desirable on a finished diamond.
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