The diamond cutting process
In their most natural form, diamonds are quite ugly. They have no luster or shine and, in fact, look like nothing more than broken glass – and that too without the glitter. A diamond must be cut and then polished before it actually becomes a thing of beauty.
Diamond cutting is both an art and a science that is intrinsic to the creation of a beautiful gemstone. The shape or size of a diamond is less important than the quality of the cutting and the skill of the cutter. The diamond cutting process involves marking, cleaving and/or sawing, bruiting, faceting, and placing and polishing.
The first step of the diamond cutting process is marking the stone. A planner examines each uncut diamond to decide how it can be cut to maximize its value. After a thorough examination of the imperfections and how they can be minimized, the planner marks the uncut stone to determine whether the stone should be cleaved (cleanly cut) and/or sawed.
If the diamond is be cleaved, it goes to the cleaver. Cleaving is a critical stage for larger, more valuable stones and needs extreme care and caution. Undue pressure can shatter the stone. The cleaver cuts along the marked line, using another diamond as a cutting tool. The stone is mounted in a dop and a steel wedge is inserted into the groove. A sharp blow to the wedge with a mallet splits the stone along its marked cleavage. A stone may need both cleaving and sawing, in which case the stone goes for sawing after the cleaving.
If cleaving is unnecessary, the stone goes for sawing. A diamond saw is a very slim bronze disk with a diamond-dust-charged rim. It rotates on a horizontal spindle at 4,000 revolutions per minute. As in the cleaving process, the sawyer mounts the stone in a dop and positions it to rest on the top of the saw blade. During the sawing process, the rim of the saw continues to recharge itself with the dust of the stone being sawed. It takes the saw somewhere between four and eight hours to cut through a 1-carat rough stone.
The next process is bruting, also called ‘rounding’ or ‘girdling’. The stone is placed in the chuck of a lathe. As it spins, another diamond mounted in a dop is held against it. The stone is slowly rounded into a conical shape.
Faceting is the process that transforms the stone into a diamond. For the standard Round Brilliant, for instance, the stone is passed to the blocker (or lapper), who is skilled at placing the first 18 key facets on the diamond. The brillianteer is another skilled worker who places and polishes the other 40 facets. Great skill and tremendous care are required at this stage.
Placing and Polishing
During this final process, the diamond is placed in a lead dop or in a mechanical clamp. It is held down on a revolving circular disk, called a lap, which has been charged with diamond dust.
The most popular style of cut is the Round Brilliant cut, a round stone with 58 facets. A Single cut, with only 18 facets, is a simpler form of cutting a round diamond. Any style of diamond cutting other than the Round Brilliant or Single cuts is called a ‘fancy cut’, or ‘fancy shape’. The most popular fancy cuts include the Marquise, Emerald, Oval, Pear, and Heart. Smaller Brilliant-cut diamonds and other small diamonds, called ‘melee’ are used in decorative mountings for larger gemstones.
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