Rough diamonds appear lusterless, coarse, and unimpressive before they are cut and ground. Only the right cut unleashes the characteristic sparkle and famous fire of a diamond. Even experts can only guess the quality, clarity, and therefore the value of a rough diamond on visual inspection.
Modern 3-D techniques now make it possible to create an exact virtual model of rough gemstones. Scanner technology can detect even internal inclusions – a key quality concern when grading diamonds. Based on this digital copy, the computer calculates how the diamond may be cut. After all, each crystal has its own perfect finish. In contrast to clarity, carat, and color, the cut of a diamond can be changed by people – and this attribute can increase the value of a desirable gemstone. An important task of experienced diamond grinders is to decide how a jewel should be cut and polished in order to reach its full potential.
In the pre-sorting stage, each and every stone is carefully examined and assessed. Before experts can begin cutting rough diamonds, each precious stone is broken apart – but how do you split the world’s hardest natural material? Today, people use either modern laser techniques or tools made of the same material: only diamond grinding wheels and abrasive paper coated with diamond powder make it possible to saw, grind, and polish rough diamonds.
Once split, each individual jewel is ground round in a process known as “bruting.” There follow several stops of careful, painstaking grinding. This stage lasts several hours and calls for a great deal of skilled craftsmanship – ultimately resulting in a perfectly shaped diamond.
The cut alone is responsible for the brilliant sparkle of a diamond. Depending on the natural shape of the rough stone, dealers must decide what form will best show off the radiant brightness of the cut diamond while also considering how to lose as little material as possible. The ideal solution is a perfectly shaped jewel with minimum waste. Typically, different kinds of facets are applied to diamonds during the cutting process. In addition to the universally known and highly sophisticated brilliant cut, these include the emerald cut, princess cut, hearts and arrows cut, marquise cut, and a number of older cuts. All cut diamonds have many smooth polished surfaces, which are called facets. These kindle the fire of a precious stone by refracting the incident light, breaking it up like a prism into the colors of the rainbow. The arrangement of facets, angular proportions, and the thickness of the girdle play a decisive role here. If the cut is too shallow or too deep, the proportions will be inconsistent and the sparkling effect diminished. Exact calculations and an even polish are absolutely essential when cutting and grinding diamonds.