The process – which, in addition to perfecting the shape of the diamond, serves to polish it – is done by hand. The quality of the cut is not only essential to determine the value of a jewel, but it also gives the stone its shine and beauty.
As diamond is the hardest material known in nature, cutting it is not a piece of cake – not to mention the high risk of damaging the very expensive stone. “Almost always the stonecutters entrusted with larger stones are over 50 years old. This is because it takes a long time to learn all the tricks of the process”, says the stonecutter Renato Santos, president of Brasil Comércio de Diamantes.
There are two ways to cut a rough diamond: in cleaving, the most common method, the diamond is split with a quick blow. On some stones, however, this technique does not work. Sawing is then used, a long and tedious process, carried out with a rotating electric saw or, more recently, with laser beams.
After cutting, comes the blocking stage, in which the diamond is scraped on another until it approaches the desired shape. The facets (as the many small faces of a diamond are called) are made in the next step, called polishing. The stone is fitted to the tip of a rod called a dop and pressed against a rotating disk coated with diamond dust. The process is somewhat reminiscent of a needle scratching a vinyl record on a record player.
In general, small diamonds are cut in a single day. As for large stones (above 20 grams) this work can take up to more than a year!