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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
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.
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.
To cut a rough stone, it is first set in a 'dop' or holder using quick drying
cement. 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
The first step in diamond cutting is the examination of the stone in the rough
form. Each stone is totally unique and so must be studied in detail in order
to determine the finished shape that will retain as much weight as possible.
The stone is then marked with India ink to indicate how it must be divided.
A diamond is found naturally in the rough form. It looks much
like a crystal and lacks any real lustre. The true brilliance and fire of the
stone is only unlocked after a number of processes described below. These processes
can all be performed by different specialists.