Cut

Primarily, "cut" refers to the shape of the stone, with the round brilliant being the most traditional. All other shapes — including princess, cushion, radiant, oval, emerald, marquise, and pear — are referred to as fancy shapes.

Cut can also indicate the style of faceting or the overall geometry of the stone’s proportions. Today, most diamonds are cut in the brilliant or modified brilliant style. Earlier cuts — shaped by the limitations of ancient tools and a limited understanding of optics — were far less precise.

It was Marcel Tolkowsky, in the early 20th century, who developed the mathematical foundation for the modern brilliant cut. His calculations optimized the movement of light through a diamond, defining the ideal number, placement, and angle of facets to maximize brilliance.

Though contemporary methods may increase the number of facets, they do not surpass the optical performance of Tolkowsky’s original proportions. The modern round brilliant consists of 58 facets, not including the culet, and is considered the standard — unless a buyer seeks an alternative like the old mine cut, European cut, or a modern.