Diamond Cut Process
The Essential 7C's
Once a full examination of each rough diamond has been carried
out, the stone is marked to decide how it should be cut to yield the
greatest value. At this stage, the shape of the rough diamond and the
number and location of imperfections must be considered. The marker or
planner must determine the direction of the cleavage (or grain) in the
diamond. Due to the diamond’s atomic structure, it can be cleaved in
four directions parallel to the octahedron crystal faces.
If the planner decides the stone should be cleaved, it then
goes to the cleaver. Large diamonds are often pre-shaped by cleaving
into pieces suitable for sawing. For stones that are considerably large
and valuable, cleaving is critical as a mistake by the planner or
cleaver could shatter the stone. Using another diamond as a cutting
tool, a groove is cut along the line showing where the stone is to be
cleaved. The cleaver mounts the diamond in a dop, or holder, inserts a
steel wedge into the groove and strikes the wedge sharply with a mallet
to split the diamond along its cleavage.
The third stage (or second if cleaving is unnecessary) is
sawing. The specialised saw is a paper-thin disc of phosphor bronze,
rotated on a horizontal spindle at about 4,000 revolutions per minute.
Mounting the diamond in a dop, the sawyer clamps the diamond so it rests
on top of the blade. The rim of the saw is charged with diamond dust,
so that as the sawing continues, the blade continues to recharge itself
with diamond from the crystal being cut. The saw is able to cut through a
1-carat rough diamond in 4 to 8 hours, but if it hits a knot, the
process may take much longer.
Today many diamonds are cut using laser equipment which is far
more accurate and efficient. The laser saw revolutionised diamond
cutting when it was introduced in the 1930s. The stone is mounted onto a
dop (similar to those used in conventional sawing) for passage through
the powerful laser beam, whilst the progress is monitored on a screen.
The burned graphite from the high-temperature laser leaves a black mark
around both sides of the stone where the laser cut through. Therefore,
these sides then need to be polished. In certain cases, more weight is
lost than would have been with conventional sawing.
The biggest advantage of laser cutting is its precision. There
is no cutting edge to wear down, and lasers are less likely to warp the
diamond because the heat is confined to such a narrow space. Since this
method causes less friction on the stone, it is also safer – although
temperatures are extremely high. Efficiency is also an advantage, as
less manual labour and higher-speed technology means speedier production
The following step is called girdling, and may also be
referred to as rounding or bruting. The stone is placed in the chuck of a
lathe and as it spins, a second diamond mounted in a dop at the end of a
long handle is held against it. This process slowly rounds the diamond
into a cone shape.
After the diamond has been girdled it is sent to the lapper,
or blocker, who specialises in placing the first 18 main facets on a
brilliant-cut diamond. Next it is sent to the brillianteer who creates
and polishes the remaining 40 facets, when the diamond is being cut in
the standard 58-facet brilliant cut. For placing and polishing, the
stone is set either in a lead dop or a mechanical clamp and held down on
a revolving cast-iron lap (a horizontal, circular disc) that has been
charged with diamond dust. Extra care is required at the faceting stage
because the angles of the facets must be exact in order to yield maximum
brilliancy, and their sizes must be accurately regulated to preserve
Once the fully faceted diamond has been inspected and
approved, it is then boiled in hydrochloric and sulphuric acids to
remove any dust and oil. It is then considered a finished, polished
diamond. Such loose diamonds are then ready to be distributed to
wholesalers, manufacturers and retailers to create products for the
diamond shopping consumer.