A jeweler should provide at least two 3rd-party certifications which prove the quality of your diamond.
The GIA report is the best and most widely used rating for diamond performance. Each report contains the dimensions of the diamond as well as a rating of performance.
The GemEx Light Performance Report measures and certifies the optical brilliance, fire and sparkle of a diamond using a patented optical spectrophotometer.
An optical scope is used to analyze the “hearts and arrows” symmetry of the diamond. This provides an indicator of the quality of the light distribution emitted by the diamond.