Cut refers to the angles and proportions of a diamond. It is the only one of the 4Cs that is influenced by the human hand.
Diamond cutting requires great skill and training. The cutter must polish tiny surfaces known as facets onto the rough diamond. This process is what creates the facets known as the crown, culet, table, girdle and pavilion of the diamond.To cut a diamond perfectly, a craftsman will often need to cut away more than 50% of the rough diamond.A well-cut diamond will internally reflect light from one mirror-like facet to another and disperse and reflect it through the top of the gem. The facets, when arranged in precise proportions, will maximize the fire life and brilliance of a diamond.A well-cut diamond will be higher in quality and value than deep or shallow-cut diamonds. Diamonds that are cut too deep or too shallow lose or leak light through the side or bottom, resulting in less brilliance and a less valuable stone. Cut also refers to the shape of a diamond – round, square, or pear, for example.Round diamonds are symmetrical and capable of reflecting nearly all the light that enters, so it is the most brilliant of all diamond shapes and follows specific proportional guidelines.Non-round shapes, also known as ‘fancy shapes’ have guidelines in order that they are considered to be well-cut.