How Diamonds are cut

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Diamond Cutting Steps

Marking

Carefully examining each diamond crystal, a master craftsman decides the cutting strategy and marks the diamond. To make this decision, the shape of the rough diamond and the number and location of imperfections must be considered. Of utmost importance is the determination of the direction of the cleavage, or grain, in the diamond crystal (because of its atomic structure, diamond can be cleaved in four directions parallel to the octahedron crystal faces). Taking these factors into account, the planner decides how the diamond should be cut and marks it to indicate where the stone should be cleaved or sawed.

Cleaving

If the planner's decision is to cleave the stone, it then goes to the cleaver. Large diamonds are often preshaped by cleaving into pieces suitable for sawing. When the stone is very large and valuable, the cleaving is a most critical process, because a mistake by the planner or the cleaver can shatter the stone. The cleaver cuts a groove along the line showing where the stone is to be cleaved, using another diamond as a cutting tool. He mounts the diamond in a holder called a dop and inserts a steel wedgeinto the groove. He strikes the wedge sharply with a mallet and the diamond splits along its cleavage.

Sawing

The third step, or the second step if cleaving is unnecessary, in the diamond-cutting process is sawing. The saw is a paper-thin disk of phosphor bronze, rotated on a horizontal spindle at about 4,000 revolutions per minute. The sawyer mounts the diamond in a dop and clamps it so that it rests on top of the blade. The rim of the saw is charged with diamond dust, and, as the sawing progresses, the blade continues to recharge itself with diamond from the crystal being cut. The saw will cut through a 1-carat rough diamond in four to six hours, unless it strikes a knot (actually a grain reversal), in which case it may take much longer, as the diamond will need to be repositioned and sawn in another direction.

Often today, diamonds are sawn with a laser saw device, which reduces sawing time by half, and is not affected by grain structure or knots.

Bruting

The next step in cutting a round stone is called bruting. The diamond to be bruted is placed in the chuck of a lathe; while it spins, a second diamond mounted in a dop on the end of a long handle is held against it, and the diamond is slowly rounded into a cone shape (actually borh diamonds are being shaped at once.)

Great care must be taken not to remove material too quickly, as this could fracture the outer part of the diamond. This is seen as Bearding in finished stones, a minute feathering of tiny cracks radiating inward from the girdle.

Faceting

From the bruter the diamond goes to the blocker, who cuts the table and culet then puts the first 4 bezel facets on the crown, and the first 4 mains on the pavillion of a brilliant-cut diamond.

Then the crossworker adds the other 4 bezel facets and 4 mains leaving a total of 18 facets at this point. On smaller stones, blocking and crossworking are often combined.

It then goes to the brillianteer, the worker who places and polishes the remaining 40 facets, if the stone is being cut in the standard 58-facet brilliant cut.

Placing and polishing are done by setting the stone either in a lead dop or a mechanical clamp and holding it down on a revolving cast-iron lap called a scaife (a horizontal, circular disk like a record turntable) that has been charged with diamond dust. Great skill is necessary at every stage, but especially during faceting, because the angles of the facets must be exact in order to yield maximum brilliancy, and their sizes must be accurately regulated to preserve symmetry. In addition, the polish must be perfect, free of polishing drag lines or burned facets.

After polishing, the diamond is boiled in acid to remove any residue, then it's done!

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(425)-485-0625.

Foxfire Jewelers
14176 NE Woodinville-Duvall Road
Woodinville, WA 98072

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