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Marking:
In this step the diamond is examined in the rough
form. Each diamond is different and it is carefully
studied before it is sent for various processing
stages. This is done to determine the shape and
weight of the diamond after the cutting and
polishing processes. The stone is then marked with
ink to indicate how it must be divided.
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Cleaving:
To cut a rough stone, it is first set in a 'dop' or
holder using quick drying cement or any other strong
adesive. Then, using another diamond, a small groove
is made along the division line. A square-edged
knife is then inserted into the groove and tapped
sharply with a mallet. It is this action that
determines the diamond's future as if the division
line has not been placed properly, or followed
accurately, the diamond can shatter. Cleaving is
always done parallel with the grain of the diamond.
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Sawing:
Sawing is the process by which a diamond is cut
against the grain. Before a diamond is sawn, it is
mounted again in a 'dop' or holder. It is then
lowered slowly on to a vertically positioned saw
spinning at high speed (up to 15,000rpm). The blade
is made of phosphor bronze and is coated with
diamond powder mixed with oil. The sawing of a large
stone can sometimes take weeks.
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Bruting:
During this stage of the process, the diamond's
girdle is formed. This is also known as girdling
or rounding. The girdle is the band which is
formed around the thickest part of the stone. To
form the girdle, the stone is again set in a 'dop'
which is in turn fixed on to the centre of a lathe
which spins at high speed. Using another diamond set
in a long 'bruting stick', the corners of the rough
stone are gradually rounded off until the spinning
diamond is perfectly round at its thickest part.
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Blocking or Cross Work:
This is the final stage in the making of a polished
diamond. It is during this time that the diamond's
facets are polished onto the stone. This is done
using a horizontally mounted circular cast iron disc
known as a scaife. The scaife is of course
impregnated with oil and diamond dust. The diamond
to be polished is set in an adjustable dop at a
certain angle and lowered onto the plate. The angle
of the diamond must be changed for each facet. On a
brilliant cut diamond there are usually 57 facets
and the
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Photos
courtesy of HRD |