Diamond cutting

Diamond cutting is the practice of changing a diamond from a rough stone into a faceted gem. Cutting diamond requires specialized knowledge, tools, equipment, and techniques because of its extreme difficulty. Diamond cutting is the practice of changing a diamond from a rough stone into a faceted gem. Cutting diamond requires specialized knowledge, tools, equipment, and techniques because of its extreme difficulty. The first guild of diamond cutters and polishers (Diamantaire) was formed in 1375 in Nuremberg, Germany, and led to the development of various types of 'cut'. This has two meanings in relation to diamonds. The first is the shape: square, oval, and so on. The second relates to the specific quality of cut within the shape, and the quality and price will vary greatly based on the cut quality. Since diamonds are one of the hardest materials, special diamond-coated surfaces are used to grind the diamond down. The first major development in diamond cutting came with the 'Point Cut' during the later half of the 14th century: the Point Cut follows the natural shape of an octahedral rough diamond crystal, eliminating some waste in the cutting process. Diamond cutting, as well as overall processing, is concentrated in a few cities around the world. The main diamond trading centers are Antwerp, Tel Aviv, and Dubai from where roughs are sent to the main processing centers of India and China. Diamonds are cut and polished in Surat, India and the Chinese cities of Guangzhou and Shenzhen. India in recent years has held between 19–31% of the world market in polished diamonds and China has held 17% of the world market share in a recent year. Another important diamond center is New York City. The diamond cutting process includes these steps; planning, cleaving or sawing, bruting, polishing, and final inspection. Diamond manufacturers analyze diamond rough from an economic perspective, with two objectives steering decisions made about how a faceted diamond will be cut. The first objective is that of maximum return on investment for the piece of diamond rough. The second is how quickly the finished diamond can be sold. Scanning devices are used to get a 3-dimensional computer model of the rough stone. Also, inclusions are photographed and placed on the 3D model, which is then used to find an optimal way to cut the stone. The process of maximizing the value of finished diamonds, from a rough diamond into a polished gemstone, is both an art and a science. The choice of cut is influenced by many factors. Market factors include the exponential increase in value of diamonds as weight increases, referred to as weight retention, and the popularity of certain shapes amongst consumers. Physical factors include the original shape of the rough stone, and location of the inclusions and flaws to be eliminated. The weight retention analysis studies the diamond rough to find the best combination of finished stones as it relates to per carat value. For instance, a 2.20-carat (440 mg) octahedron may produce (i) either two half-carat (100 mg) diamonds whose combined value may be higher than that of (ii) a 0.80-carat (160 mg) diamond plus a 0.30-carat (60 mg) diamond that could be cut from the same rough diamond. The round brilliant cut and square brilliant cuts are preferred when the crystal is an octahedron, as often two stones may be cut from one such crystal. Oddly shaped crystals, such as macles are more likely to be cut in a fancy cut—that is, a cut other than the round brilliant—which the particular crystal shape lends itself to. Even with modern techniques, the cutting and polishing of a diamond crystal always results in a dramatic loss of weight, about 50%. Sometimes the cutters compromise and accept lesser proportions and symmetry in order to avoid inclusions or to preserve the weight. Since the per-carat price of a diamond shifts around key milestones (such as 1.00 carat), many one-carat (200 mg) diamonds are the result of compromising Cut quality for Carat weight.