The Princess Cut, which today is the second most popular shape for diamonds after the round brilliant, is of relatively recent vintage, having been developed in Israel in the late 1970s. With a face-up shape that is square or rectangular, it has side-on shape of an inverted pyramid, providing it will a profile that is not dissimilar to that of the round cut.
They are popular among diamond manufacturers because they characteristically provide a significantly greater yield than round stones, meaning that less rough material is sacrificed during the production process. But also, because their girdle has straight sides, they can be more easily used in a jewelry requiring multiple sets of diamonds, using invisible or channel settings.
The cut was developed by Betzalel Ambar, Israel Itzkowitz and Igal Perlman in Israel in 1979, and was inspired by the Radiant Cut, created by Henry Grossbard several years earlier, which is a square-shaped diamond with cut-off corners that approaches the brilliance of a round. The developers of the Princess Cut looked to create a shape that would dazzle like the Radiant Cut, but would allow stones to be set flush against each other, without any apparent gaps.
The original version was a square brilliant with 49 facets. The creators, who has patented the design, wanted to sell it as a trademarked cut, but discovered that they could not do that with the name Princess. Consequently, it was registered as the Quadrillion. What made it unique was that, unlike most other shapes, the lower-pavilion facets widened towards the culet, instead of narrowing. This created a star-like effect on the crown.
The Quadrillion was an immediate success, and versions of the cut were soon being turned out by other manufacturers, who invariably added facets. These popularly became known as Princess Cuts.
The crown of the Princess Cut has one of two basic styles: bezel corners with a small diamond shaped facet from the corner of the table to the corner of the girdle, and French corners where the star facets point to the stone corners and usually extend about 50 percent of the distance from the corner of the table to the corner of the girdle.
The Princess Cut has two sets of main crown facets and two sets of main pavilion facets, in contrast to rounds, which has only one each.
Different versions of the Princess Cut have pavilion configurations of two, three, or four tiers of chevron facets, and larger stones sometimes have even more. The addition of chevron tiers typically increases the brilliance of the stone.
The girdle corners meet at right angles, they are the most delicate part of the stone. To avoid chipping, they are sometimes cut with very small facets, which is a technique known as “chamfering.”
While Princess Cuts are not necessarily square, the Gemological Institute of America (GIA) warns that they should not have a length-to-width ratio not exceeding 1:1.05. Princess cuts that have uneven sides or unequal proportions are less attractive, GIA says.
GIA also notes that she symmetry of the facets are important and can be examined by drawing an imaginary line down the length of the diamond, and seeing if the facets on the right and left halves are the same shape and size. Also, a balanced contrast of light and dark patterns in the table and facets are important.