Diamonds are cut using blades, lasers or other diamonds with techniques that include cleaving, sawing and bruting. During the cutting process, a diamond can lose up to 50 percent of its original weight.
The four steps of diamond cutting are planning, cleaving or sawing, bruting and polishing. To cleave a diamond, a wax or cement mold holds the diamond in place while the cutter carves a sharp groove along the diamond's internal lateral planes, where the diamond is weakest. The cutter then places a steel blade in the groove and forcefully strikes it, essentially breaking apart the diamond.
Sometimes, diamonds have to be cut where there is no plane of weakness, and this cannot be done with cleaving, so the cutter uses a saw. The saw contains a blade that rotates at high speed. This technique gives diamonds their shape. Lasers can also be used to saw diamonds, but the process takes much longer.
When diamonds are cut by hand, in the technique known as bruting, the cutter uses another diamond. The diamond to be cut is inserted in cement with one corner exposed, and the cutter then rubs the exposed diamond parts together to cut the raw diamond. To create the diamond's finished look, during the polishing phase, the cutter places the diamond onto a polishing wheel that is coated with an abrasive diamond powder. The abrasive powder smooths the diamond as the diamond scrapes against the wheel.