After eight years of study, the Gemological Institute of America has issued the first of a series of reports on diamond cut (see accompanying article). The study offers some fascinating mathematical data. But with only one-third of the project complete, the report makes some hasty judgments on cut-grading systems already in place. GIA’s initial report literally lacks fire (discussion of spectral colors, or dispersion) and sparkle (discussion of brilliance and fire in motion, or scintillation). Using mathematical models and computer ray tracing, GIA’s researchers have unleashed an incredi