Brilliance+ Index

The Leon Mege exclusive Brilliance+ Index compares round diamonds by evaluating the data on the GIA certificates. We can predict the diamond’s light performance and brilliance thanks to the proprietary algorithm developed through extensive scientific research. Through the miracle of scientific observations, we created a revolutionary system that calculates the complicated interaction of light with diamond facets and assigns a numeric value.

On a hunt for "Super Ideal"

Evaluated metrics

  • Crown angle
  • Pavilion angle
  • Table
  • Total depth

The calculation is based on the stone’s table, height percentage, and angles of the crown and pavilion listed on a GIA diamond certificate. Carat weight has no bearing on the light return and is not required. The girdle thickness does not affect the light return, but an extremely thick or thin girdle requires careful consideration.

Necessary parameters for Diamond Cut Evaluation Index

The Brilliance+ score is handy for breaking a tie between identical ideal-cut round diamonds. We evaluate the cut grade of any modern round brilliant based on its GIA data. The index is measured on a scale of 0 to 100. Grades within 5 points are nearly identical and do not indicate any advantage over one another. In practice,  the maximum grade rarely exceeds 96-97. 

The great majority of commercially available round brilliants score below 50. Only a small fraction of round diamonds receive “excellent” -cut, -polish, and -symmetry grades from the GIA. These XXX diamonds score above 50. About 10 percent of GIA XXX diamonds score above 75. In the diamond trade, these stones are called “super-ideal.”

Brilliance+ vs. HCA
Brilliance+ vs. HCA

Superior to HCA

Leon Mege Brilliance+ index is superior to the HCA score promoted by Pricescope Cartel. When evaluating a diamond, Brilliance+ is just one step among many we use to reject poor performers. Only GIA-graded round brilliants with XXX grades are eligible for the evaluation. Grades and measurements by gem labs other than the GIA are inconsistent and unreliable. To evaluate a GIA diamond, we ask for a retainer. Results are typically returned the same day.

Brilliance at a bargain

The index is not a reflection of the stone’s beauty. Even a diamond with a low score can be quite beautiful. Moreover, an untrained eye cannot tell the difference between two GIA-certified XXX diamonds, regardless of their score.

The index is designed to highlight the minute differences in the cut and potentially spot a better deal using the Brilliance+ index in conjunction with minor price fluctuations. Brilliance+ is a consumer version of our exclusive 23-point evaluation system used to handpick diamonds for our clients. The index is a simple way to break a tie between several nearly identical stones without becoming a gemologist. It will help to make sense of contradicting information often found online.

Light return illustration by Leon Mege

Analyzing Light Performance

In diamonds, the reflected light returns as brilliance, the light separated into rainbow colors is returned as fire, and rapid changes from dark to bright light make up scintillation (sometimes called sparkle). A diamond is not a motionless object; it is observed from thousands of angles. Evaluating light return from only one angle will not give a clear picture of its strength.

Different patented gizmos claim the ability to measure the light return from multiple lighting positions, such as BrillianceScope® Analyzer. Unfortunately, none of them come close to a human eye of a professional gemologist.

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