Diamond cutting is the practice of converting a rough diamond into a faceted and polished gemstone or gemstones. When performed by an experienced professional, diamond cutting significantly enhances the value of the stone, especially in the case of large diamonds, but it is also easy to make a mistake which could utterly ruin the diamond. Diamond cutters traditionally train in apprenticeships, learning from master diamond cutters who are often family members.
Diamond specialists are sometimes referred to as a diamantaires. A diamantaire may be a diamond cutter, or a dealer. In either case, he or she knows everything there is to know about diamonds. A diamantaire can look at a rough diamond and see the potential in the stone, and can assess a cut and polished diamond for color, cut, clarity, and carat size, looking for the famous “Four Cs” which determine the price a diamond can fetch on the market.
People have been mining, cutting, and polishing diamonds for thousands of years. Historically, the focus was on retaining high carat sizes, sometimes at the cost of brilliance. Old fashioned cuts may be large with minimal wastage, but they can produce dulled stones. Modern diamond cutting tries to minimize waste, but it is also focused on the creation of a stone which is lustrous and brilliant, and sometimes this requires cutting 60% or more of the rough away.
The process of diamond cutting starts with planning. For small stones, planning usually consists of checking the stone for obvious flaws and selecting a cut best suited to the shape. For larger stones and so-called fancy diamonds, the planning process is more complex. In the case of fancy diamonds, color retention is an important aspect of the cutting process. Thinking about flaws in the stone is also critical, as is developing a cut which will reflect light to create the brilliance associated with diamonds. Some stones require custom cuts, rather than generic ones, and a great deal of math is involved in the planning stages.
Next, the stone is sawed or cleaved along an existing flaw to cut it into a rough shape. Sometimes, a large stone will be broken into several pieces for cutting and polishing separately, while in other cases, large chunks of rough are removed during this stage. Next, the diamond is bruted or girdled, a process in which the stone is rubbed against another diamond to develop a facet. This process can develop friction and high heat, so stones may be cooled during the girdling process to prevent cracking. After girdling, the diamond can be polished, washed, and sold.
This delicate diamond cutting process is only used for gem-quality diamonds, as industrial diamonds do not need to be prepared with such careful attention. Some diamond cutters handle stones other than diamonds, such as emeralds and rubies, while others focus solely on working with diamonds.