21st Century Certificate for $21: Performance Specifications & Repeatibility

Repeatability:+/- 0.005mm with 2 Sigma probability for linear measurements for all sizes except for table. Repeatability for angles depends on size of stone

Color: +/- 1/3rd of a color grade with 2 Sigma probability

Fluorescence: +/- 1/3rd of a fluorescence grade with 2 Sigma probability

Light Behavior: Brilliance +/- 2%, Sparkle +/- 2% and Intensity +/- 4 % with 98% probability

Repeatability of Clarity Grades: +/- ½ of a Clarity grade with 2 Sigma probability