Diamond Education: Why Lab Report “Numbers” Don’t Tell You What You Need To Know

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Consumers are constantly asking for assistance on whether they should purchase a diamond based on the “numbers” provided by the diamond lab grading report. The two best diamond grading labs are the GIA and the AGS, noted for their accuracy and consistency.

While the diamond lab grading report is very useful, it does not give the entire story and it is helpful to get additional information that analyzes the level of Cut precision and light performance of the diamond.

Two current technologies that provides these assessments are the Megascope Proportion Analyzer for Cut and the Brilliancescope for Light performance.

To illustrate this point we have attached data from two diamonds: A .78 carat GIA graded EX-EX “Ideal Cut”, the second is a 1.51 carat GIA graded diamond that has a Table percentage that is greater than its Depth percentage, a situation that in many instances can lead to significant light leakage out of the diamond instead of light being maximally refracted to your eye. In the trade this type of configuration is known as a “fish-eye”.

The results shown below are opposite to expectation. The EX-EX Ideal cut diamond displays poor to mediocre light performance as measured by the Brilliancescope whereas the diamond with the ‘poorer’ numbers displays excellent and evenly distributed light performance.

It is important to note that the round brilliant shape consists of 58 facets and their cut angle, size, and proper alignment critically impacts visual beauty and light performance. The “numbers” on a diamond lab grading are averages only and do not address facet alignment.

For those consumers shopping for diamonds on Internet websites and not physically able to examine the stones, the more information you get, the better purchase decision you will make.