What You Need to Know About a GemEx Rating

What is a GemEx Rating?

By now, you may be familiar with a number of diamond certifications and laboratories. One particular name that you may have encountered is GemEx. What distinguishes a GemEx rating is the assessment of light performance, aka the way a diamond glitters and sparkles when light passes through.

The rating provided, specifically known as GemEx Light Performance, is evaluated against three main criteria:
  • Brilliance (white light)
  • Fire (colored light)
  • Sparkle (the flickering light emitted at different angles)

All three of these qualities will be represented in a bar graph that measures against how other diamonds of the same shape rank. There should also be a depiction of the unique diamond included in the report that illustrates its symmetry.

How is the Rating Determined?

GemEx has created a patented imaging spectrophometer that diamond producers use to evaluate their cut diamonds before being shipped to jewelry stores. Once a diamond has been shaped and polished, the device is used to measure performance (brilliance, fire and sparkle). If the diamond meets the producer's standards, it is sent on its way. Only when a quality assurance specialist confirms the rating produced is legitimate will an official GemEx certificate given.

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