Articles about Diamond Grading

Dimensioning Diamonds

There have been inconsistencies and vagueness about how diamond dimensions are defined. This clarifies the terms and differences and suggests better alternatives.

Why are the ‘Best’ Cuts on the Edge of the Table-Bezel Zone?

Garry Holloway1 was the first to suggest a meaningful explanation for this: he suggested that, because there is a small difference between pavilion main & half facet slopes (less than 2º in a typical round brilliant), this may cause one to be dark when the other is bright – producing contrast in the gem’s image. Studies of human optical response2 say that this is attractive to viewers; it may be why the people Tolkowsky polled chose the proportions they did.


AGS Laboratories - Clarity Grading of Diamonds

Diamond clarity grading involves assessing how readily visible the inclusions are in a diamond and accounting for an extensive list of potential variables including the size, number, type, location, and relief of its inclusions. At the American Gem Society Laboratories (AGSL), clarity grading begins once color grading is completed.

How to Evaluate a Fancy Vivid Yellow Diamond

Fancy Vivid Yellow - "The King of Yellow Diamonds." This article will delve into the world of these most highly prized yellow diamonds.

AGS Laboratories - Color Grading of Diamonds

A diamond’s color (or lack thereof) is a critical aspect in determining its market value. Grading the color is therefore a crucial part of the laboratory certification process. The following article will illuminate the various steps and considerations in performing color grading at the AGSL.