Diamond is the hardest substance on earth, rating a perfect 10 on Moh's hardness scale. Only another diamond is hard enough to cut one. The art of diamond-cutting has existed for hundreds of years and the techniques used today are essentially the same as the original practices. Some of the tools, of course, have even more precise features and a more modern appearance.
The single most important innovation in diamond cutting tools was the scaif, which was invented in 1456 by Flemish jeweler Lodewyk van Berken. The scaif is a polishing wheel infused with olive oil and diamond dust that allows gems to be polished on every facet at the best angles. The scaif single-handedly revolutionized diamond cutting and made diamonds useful for popular applications like jewelry making. It essentially created the retail market for diamonds. The idea that diamond dust can be used to increase the cutting power of blades has been widely adapted, and remains a central feature of modern diamond cutting equipment, which uses electricity to power machines and computers to guide cutting.
The process of transforming a rough diamond into a jewel is truly an art, and progresses in stages. After spending significant time planning a design based on the diamond's natural features and color, a rough diamond may be cleaved along its natural grain if there are impurities that prevent it from being used. The diamond is then sawed into the general shape of its final design, but without any facets. It is then attached to a lathe and ground down by another diamond. Finally, an electric version of a scaif is used to apply the multiple facets that give cut diamonds their unique luminous properties. At each step of the process, diamond-tipped tools are employed to produce the finished jewels.
Bruting is the name of the step of rounding a diamond into a conical shape using a lathe and rubbing it against another diamond until it takes on the desired dimensions. Modern autobruting is done using computer software and laser sensors to apply just the right amount of pressure to achieve the perfect shape. Bruting is, in effect, the first cut of a diamond, establishing the basic shape of the finished gem.
Commercial diamonds are known for their myriad intricate facets. To achieve these, modern diamond cutters can choose from a number of electric semi-automated faceting machines such as the Poly-Metric Scintillator, the Facetron, and the Cabochon Grinder. While holding the gems at the end of wooden dowels called dops, the skilled craftsman executes the final stage of the original design by pressing them against the buffing surfaces of the machines, whose speeds are controlled electronically. Water is passed over the surfaces to reduce the heat of friction. To keep a close eye on their progress, cutters use the classic magnifying monocle, called a loupe.
Much of professional diamond cutting occurs outside the United States, but that doesn't keep the approximately 17,000 amateur faceters in America from their chosen hobby. Effective diamond cutting tools like the Facetron can be obtained for under $2,500 with many of the features used by the pros. This single all-in-one tool can perform all the essential diamond-cutting tasks, and can be used to cut all kinds of gems.