Gemological Institute of America, Inc.

James E Shigley

Gilbert Norman Ravich

Mary L Johnson

Shane Elen

Thomas Scott Hemphill

Ilene M Reinitz

Thomas S Hemphill

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&#x2014;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.

Systems and methods for evaluating the appearance of a gemstone

Of the 'four C's,' cut has historically been the most complex to understand and assess. This application presents a three-dimensional mathematical model to 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&#x2014;called DCLR&#x2014;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.

System and methods for evaluating the appearance of a gemstone

A gem identifying device using filtered transmitted light for use in distinguishing type-I colorless diamonds from type II colorless diamonds, and natural diamonds and gems from synthetic or treated diamonds and gems.

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Temecula, CA, United States of America

James E Shigley