Color Grading "D-to-Z" Diamonds at the GIA Laboratory

ence between G and H color for a one carat roundbrilliant diamond of VS1 clarity was about 16% in both Idex and Rapaport.As part of its educational program, GIA has taught the basics of color grading D-to-Z diamonds since the early 1950s.And in the more than five decades since the GIA Laboratory issued its first diamond grading report in 1955 (Shuster, 2003), it has issued reports for millions of diamonds using the D-to-Z system.Throughout this period, GIA has experienced increased demand for its diamond grading services over a growing range of diamond sizes, cutting styles, and color appearances.This has required a continual evolution in the equipment and methods used in the GIA Laboratory, while maintaining the integrity of the grading system itself.At the core of the system's development has been an ongoing assessment of how best to observe a diamond in order to describe its color consistently.At times, the resulting adjustments have appeared to conflict with earlier statements.