Cutting Diamonds
  Marking
the Diamond
The first step in the cutting process is study. The expert examines
the diamond through a powerful magnifying glass or "loupe" (shown
above) to see how the stone can be cut to retain as much of the original
weight as possible. After studying to eliminate imperfections, he
then marks the diamond with india ink to indicate where it must be
divided.
 Diamonds
for Sawing
Each diamond has a grain, like that of wood, apparent to an expert.
In most diamonds, the first division is against the grain, and so
it is made by sawing. The diamond is mounted in a holder called
a "dop." In this picture, the four loose stones are all marked for
sawing, and the three larger diamonds are in dops, with markings
visible. The dop at the lower right holds one part of a diamond
after sawing, the other part is to the left.
 Sawing
a Diamond
The holder with its diamond is clamped into an arm above the saw
so that the blade will cut along the marked line. The phosphor-bronze
saw blade, only 35/10,000ths of an inch thick, has an edge on which
a paste of diamond dust and olive oil creates a cutting surface.
The blade turns at high speed, and the diamond is held against it
by gravity, sinking as the blade cuts through. Small diamonds take
hours to be sawed, while large diamonds can take days.
 Cleaving
a Diamond
If the diamond is to be divided with its grain to remove an inclusion,
it is set into a dop and a groove is scratched into it with another
diamond. Only a diamond can scratch a diamond. The cleaving knife,
a special blade of steel, is set into the groove and is tapped lightly
with a palm wood hammer. If properly marked the diamond splits cleanly.
If not, the tap of the mallet can shatter the stone.
 Cleaved
Diamond
When the cutter has properly studied the diamond, it will cleave
into two clean pieces like those shown here. Some of the famous
diamonds that have been cleaved are: the 3,106-carat Cullinan, the
995.20-carat Excelsior and the 726-carat Jonker.
 Girdling
the Diamond
After the diamond is cleaved, each part is finished as a separate
gem. The next step, "girdling" or "bruting," shapes the diamond
at its greatest width. For the round or "brilliant" cut, this is
done by mounting the stone on a lathe that revolves at high speed
and rounding it with another diamond held on a long stick. Diamonds
to be finished in other shapes - marquise, oval, pear shape, emerald-cut
and others - also are girdled but by a different process.
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