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What Is a GemEx Rating and Why Does it Matter?

This method of analyzing a diamond scientifically studies and rates a diamond’s “light performance” — how light shines through the stone.

You’ve seen it. A coworker is making an animated presentation. A friend is telling an exciting story. Some women are having lunch at a nearby table. And as their hands move you notice a flash of light — almost like the flash of a camera. It’s likely the play of light through a diamond as a woman’s hand moves in the air.

That play of light is what makes one diamond more noticeable than another, and it’s what led to a light performance measurement system by GemEx Systems Inc.

GemEx does not sell loose diamonds; rather it helps you choose a diamond based on how its characteristics allow light to pass through it and create that flash that caught your attention in the first place.

In a nutshell, GemEx says a diamond’s beauty is determined by the way it reflects and refracts light. Different from evaluating color, cut, clarity and carat weight, like some other diamond grading reports, the GemEx Light Performance™ Certificate measures the light a diamond returns based on three variables:

  • Brilliance: white light
  • Fire: color light
  • Sparkle: scintillation, the points of light that seemingly turn on and off as the diamond or lighting source moves

In other words, GemEx doesn’t predict how a diamond will look as light moves through it; rather, it scientifically, objectively and independently measures how light performs in a diamond. The GemEx certificate looks different from other grading reports you may see. It includes:

  1. A graph with one bar each for brilliance, fire and sparkle. The bars show how the diamond you are considering compares with all other diamonds of the same shape. The comparisons are based on measurements of more than 3 million diamonds to determine the range of brilliance, fire and sparkle possible for diamonds of the same shape.
  2. Five light measurements are taken to show how the diamond you are considering plays with light. GemEx uses a high-tech instrument called a BrillianceScope® Analyzer to evaluate the percentage of white light and color light the diamond returns as well as scintillation. To ensure accuracy, GemEx measures every diamond at multiple light angles.
  3. Also included is an image that shows the craftsmanship and symmetry of the diamond. You can match your diamond and the one pictured on the certificate using the BrillianceScope.

The Equipment

The BrillianceScope Analyzer is the commercial name of a patented device known generically as an imaging spectrophotometer. Most BrillianceScopes are installed in diamond-cutting factories. When the cutting process is finished and the diamond is ready to be shipped, it’s examined with the BrillianceScope and either sent on its way to be set in an engagement ring at a jewelry store or, if the light performance doesn’t measure up to expectations, returned to the polishing wheel for further work.

Once the evaluation is complete, quality-assurance managers examine each scan to make sure the results are valid. When the managers confirm the results, a Light Performance Certificate is printed and matched with your diamond.

The BrillianceScope does not evaluate treatments that may have enhanced the appearance of a diamond. However, a treatment may affect light performance so that would still be reflected in the measurements. GemEx measures diamonds up to 12 millimeters (close to a 6-carat round diamond) with the BrillianceScope.

Additional GemEx programs

Get comfortable at home

With GemEx Live Report, you can view an interactive version of the GemEx Certificate of a diamond you are considering. You simply enter the diamond number and certificate number and you’ll be able to examine the diamond’s brilliance, fire and sparkle without the salesperson standing beside you. To help with your buying decision, you can even share the diamond’s Light Performance Certificate with family and friends for their opinions. You can use your home computer or download an app and send the certificate to your smartphone.

Get personal

You can personalize your diamond with GemEx ION technology, which adds a unique holographic image or message that is invisible to the naked eye. Options include a picture, graphic, personal message, wedding date, birthdate and children’s names. This not only personalizes your diamond but also identifies it. GemEx maintains a secure record of your diamond and ensures that no one else can have your exact personalization. You can even show off the ION personalization with a viewer that’s included with each engraving order. The engraving does not affect the diamond’s light return performance.

Get registered

Once you purchase a diamond with a GemEx certificate, you can register it on the GemEx International Diamond Registry. The information remains available even if you lose your copy, plus you then qualify for insurance discounts through Jewelers Mutual Insurance.     

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