How to read a gemstone certificate

Your IGI diamond certificate contains a wealth of information. Here’s how to interpret every section and what to look for.

The report number

Every IGI certificate has a unique identification number at the top. This number lets you verify the certificate’s authenticity on the IGI website. It also links to a digital copy of the report that you can access anytime.

Section by section

Shape and cutting style

Identifies the stone’s shape (round brilliant, oval, emerald cut, etc.) and the faceting pattern. “Modified brilliant” means the stone has the general brilliance of a round-cut diamond adapted to a different outline shape.

Measurements

The exact dimensions in millimeters (length × width × depth). For round stones, the first two numbers should be very close to each other — a large difference indicates an asymmetric stone.

4Cs grades

Carat weight (to the hundredth), color grade (D–Z scale), clarity grade (FL through I3), and cut grade (Excellent to Poor). For Mercury & Sol diamonds, you’ll typically see Excellent cut, high color grades (D–G), and high clarity (VVS–VS).

Proportions diagram

A cross-section showing the diamond’s angles and percentages — table size, crown angle, pavilion depth, girdle thickness. These proportions determine how well the diamond captures and returns light. “Excellent” cut grade means these proportions are in the ideal range.

Clarity plot

A diagram marking the location and type of any inclusions. Green marks indicate internal inclusions, red marks indicate surface blemishes. In VVS and VS grades, these features are extremely minor and invisible to the naked eye.

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