The Round Diamond

A round brilliant diamond is actually shaped like a cone, with a curved top (known among jewelers as “the crown”) that expands to a wider base, and then tapers downwards to a sharp point.

This design was developed in the 17th century by Ambassador Julian Cardinal Mazarin (in fact, the first round brilliants were called Mazarins). To create maximum shine, he shaped the diamond to have 17 flat surfaces, called facets, which would reflect light from all sides. Another noted jeweler, Vincent Peruzzi, introduced 33 facets.

But it was Marcel Tolkowsky who was able to devise a precise and thorough mathematical model for Mazarin’s design. Using geometrical calculations, he discovered that a 58-facet cut would create the maximum amount of brilliance, and then identified the perfect proportions of the crown, diameter and base.