We are constantly asked by Consumers to evaluate diamonds for them solely based on the “numbers” provided by the Laboratory certificate and the Cert’s designation of the diamonds Polish and Symmetry. In our opinion, assessment of the “numbers” are important in describing external symmetry but can be limiting in that they do not tell you anything about the diamonds optical symmetry and Light Performance.
Light Performance is what you’re buying and what you and everyone will notice.
We have published a tutorial on the importance of using Diamond Light Performance as a tool to base your purchase decisions.
Read it Here: Diamond Light Performance
We were asked yesterday whether in round shape diamonds a Symmetry designation of “Very Good” on a GIA Report is a negative and drop-off compared to a symmetry designation of “Excellent”.
The answer is that Symmetry as shown on the GIA Cert refers to external meet-point symmetry, not optical symmetry or Light Performance.
The red arrows in the attached graphic show you the meet-points that are examined by GIA graders.
Red Arrows show the “Meet-Points” that determine the level of Symmetry.
To receive “Excellent” they must meet exactly and the meet-points of the Table – to – Crown – to – Pavillion must align exactly to each of the arrowed points. The difference between “Excellent” to “Very Good is indeed miniscule and microscopic and is something that no one will see or realize.
This external meet-point symmetry has absolutely no bearing on the diamonds light performance, which is what ultimately you are buying. No one will ‘see’ if the symmetry is “Excellent” or “Very Good” but you, and they, will definitely notice whether or not the diamond sparkles with light.
I’ve included two graphics showing Ideal Cut diamonds; one that we called in for a client and the other (our own SuperbCert H&A Diamond with Very Good Symmetry). Compare the light performance as measured by the Brilliancescope(www.gemex.com)of the diamond with “Excellent” symmetry to the light performance of the diamond with ‘only’ Very Good Symmetry. There are visibly dramatic and significant differences in Light Performance.
Ideal-Cut Diamond with “Excellent” Symmetry but poor-mediocre Light Performance as measured by Gemex’s Brilliancescope Light Performance Analyzer.
Ideal-Cut Diamond with only “Very-Good” Symmetry but Superb Light Performance.
There are over 750,000 diamonds in the Gemex Database that have been scanned and evaluated for Light Performance. We have been using this technology for the past four years and find it an important tool for evaluating diamonds.