Systems and methods for evaluating the appearance of a gemstone

Abstract

Of the “four C's,” cut has historically been the most complex to understand and assess. This application presents a three-dimensional mathematical model o study the interaction of light with a fully faceted, colorless, symmetrical round-brilliant-cut diamond. With this model, one can analyze how various appearance factors (brilliance, fire, and scintillation) depend on proportions. The model generates images and a numerical measurement of the optical efficiency of the round brilliant-called DCLR—which approximates overall fire. DCLR values change with variations in cut proportions, in particular crown angle, pavilion angle, table size, star facet length, culet size, and lower girdle facet length. The invention describes many combinations of proportions with equal or higher DCLR than “Ideal” cuts, and these DCLR ratings may be balanced with other factors such as brilliance and scintillation to provide a cut grade for an existing diamond or a cut analysis for prospective cut of diamond rough.

1 . A method of providing target proportions for cutting a diamond comprising: 
 determining the size of an uncut gemstone;    comparing a list of possible cut proportions of the gemstone with a list of proportion grades that depend, at least in part, on a calculation of dispersed color light return;    providing a target proportion for the gemstone based on said list of proportion grades.    
     
     
         2 . A method of cutting a diamond comprising: 
 determining the size of an uncut diamond;    determining a possible cut proportion for the diamond;    comparing said possible cut proportion with a list of proportion grades that depend, at    least in part, on a calculation of dispersed color light return;    cutting the uncut diamond.    
     
     
         3 - 110 . (canceled)