GIA Symposium 2006 - Fancy Color Diamonds and Cut

On August 26, Sergey Sivovolenko and Yuri Shelementiev presented "Fancy-Color Diamonds: Better Color Appearance by Optimizing Cut" at the Gemological Institute of America's Gemological Research Conference just prior to the GIA 2006 Symposium in San Diego CA.

Shelementiev was the primary speaker. The presentation was based on the premise that for every particular rough diamond piece there are restricted choices of possible shapes that can be used to obtain the fancy color grade, depending on size and spectrum.

Shelementiev said the process for the best balance of yield and color involves scanning rough and recording its absorption through pairs of parallel windows. Prospective shapes are then considered using average light path and photorealistic images, generated in special software called DiamCalc, produced by OctoNus. These images allow the user to see the level of brightness, saturation and contrast in different lighting conditions, allowing optimization of the subject rough.

Both Shelementiev and Sivovolenko emphasize that it is advisable to use several controlled lighting conditions when designing and optimizing new cuts. In addition to the process of rough planning, they showed different configurations (actual and modeled) under magna colorscope illumination and without illumination to demonstrate brightness, saturation and contrast levels. Five shapes were considered; round, princess, radiant, oval and triangle, and modeled in special edition of DiamCalc geared for cut optimization which uses a specialized color metric for brightness, chroma & saturation.