Just as the English brilliant cut, because of its 28 fewer facets, has less sparkle than the standard brilliant cut, the step brilliant, with its 20 additional facets, has greater sparkle.
The step brilliant cut is a complicated modification of the standard brilliant. With an additional 12 facets in the crown and 8 in the pavilion, the step brilliant has 78 facets, compared with the 58 of the standard.
Various kinds of cuts have been devised for special purposes in jewelry design. These include the pentagon (1), lozenge (2), hexagon (3), cut-corner triangle (4), kite (5), keystone (6), epaulet (7), baguette (8), trapeze (9) and square (10).
With this typical trim saw, water is used as a coolant for the rapidly rotating metal disk, which has a diamond-impregnated rim. Here, the blade is cutting its way through a piece of gem tourmaline.
In general, there are three operations in preparing a gemstone from the rough—sawing, grinding, and polishing. Sawing usually is accomplished by using a thin, diamond-impregnated, rapidly rotating disk of soft iron or bronze, with oil or water being used as a coolant. The very hard diamond dust literally scratches its way through the stone. Once the stone is sawed to shape, the facets are ground and polished on a rotating horizontal disk by the use of various abrasives. For rough grinding, silicon carbide—or sometimes diamond powder—is used. Scratches are removed and a high polish is given by the use of tin oxide, pumice, rouge, or other fine-grained abrasives. The thick disks, or laps, are made of cast iron, copper, lead, pewter, wood, cloth, leather, and certain other materials. Since each species of gemstone differs in its characteristics, each must be treated somewhat differently as to sawing and lapping speeds, kind of lap, and choice of abrasives. Because of the greatly increased interest in gem cutting as a hobby and the large number of amateur cutters, a substantial market has developed in the United States for lapidary supplies and equipment. New kinds of machinery, new abrasives, and new kinds of saws and laps are introduced regularly. Fundamentally, however, the process still involves sawing, grinding, and polishing.
