The Brilliant Cut is a type of jewellery cut (not a name for a type of diamond as some might think), characterized by 57 to 58 facets on two levels: the upper level, which is the crown, and the lower level, which is the conical shape. These two levels are separated by the girdle, which determines the diameter of the gem. There are calculations for the ratio between the width of the table, which is the flat face of the gem on top, and the diameter of this girdle - i.e., the diameter of the gem. The angles have been calculated with high precision to ensure maximum light dispersion, giving the gem an exceptional sparkle when light reflects off it into the viewer's eye.
The most renowned figures known for their unique contributions to this type of cut are the Italian Vincenzo Peruzzi, the American Henry Morse, and the Russian mathematician Marcel Tolkowsky.
Source: "Die Welt der Edelsteine" : World of Gemstones
Written by: Gavin Linsell