Oh, patents! Wueste's princess cut diamond

Copyright © Françoise Herrmann

The princess cut diamond is sometimes referred to as a square/rectangular modified brilliant-cut diamond, per the GIA (Gemological Institute of America) grading reports. It may be cut as a square or a rectangle. In general, square/rectangular princess cut diamonds use more of the rough diamond than round brilliant-cut diamonds. In turn, the amount of rough diamond waste that is generated impacts pricing. 

The princess cut diamond is recited in US6745596B2, titled Princess cut diamond, granted to Robert J. Wueste. Within the long prior art of diamond cutting, where round brilliant diamond cutters are always seeking the perfect diamond geometry in view of enhancing the diamond’s most prized properties, its essential brilliance, fire and scintillation, Wueste seeks to do likewise for the princess cut. Wueste seeks to find the perfect balance of the diamond’s essential properties, increasing the number of facets, recombining the shape of the crown, girdle and pavilion and their characteristic dimensions.

Wueste’s princess cut diamond has 101 facets (including the table) as summarized in the following abstract of the patent:

A princess cut gemstone having a pavilion, a girdle, and a crown. In the presently preferred embodiment, the princess cut gemstone is a diamond with 101 facets: a pavilion of 64 facets, a girdle of 4 facets, and a crown with 33 facets (including the table). [Abstract US6745596B2]

More specifically, in the preferred embodiment,  Wueste’s princess cut diamond  “comprises 8 side crown facets, 24-star crown facets, and a table facet. The pavilion comprises 20 side pavilion facets and 44-star pavilion facets. The girdle comprises 4 girdle facets".

Typical dimension ranges of a princess cut diamond are recited per the following table, extracted from the patent. Wueste’s preferred, and recited dimension ranges, for the patented princess cut diamond, are added in a fourth column --just in case you are wondering what the differences might be.

Name	Dimension	Value range	Wueste value range
Crown height  (percentage)	Percentage of crown's height to the overall width of the diamond	-5%-15%	8%  - 14%
Table percentage	Percentage of table's, vidth to the overall width of the diamond	-56%--82%	65%-85%
Depth percentage	Ratio of the overall depth of the diamond to the overall width of the diamond	-53%--85%	62%-75%
Length-to-Width Ratio	Ratio of the overall length of the diamond to the overall width of the diamond	-1:1-1.5:1	1:1-1 – 1:3-1

The patent also recites all the preferred angles for each of the crown, girdle and pavilion facets. Wueste also notes that since these are preferred dimensions and geometries, many variations, known to those skilled in the art, also fall within the scope of the invention.

The patent figure 3B is included above. It shows a bottom view of the invention square princess cut diamond, with the 44-star cut pavillion, according to the specifications of the patent. Figure 2B of the prior art is also included below it for you to see the bottom view differences in cut between the prior art 50-faceted (table included) conventional square princess cut, and the present invention reciting Wueste's 101-faceted princess cut diamond. An image of a marketed square princess cut diamond is also included above.