Glossary

With the release of the new diamond cut grading system, AGS Laboratories added new terms to the diamond industry lexicon. Below is a primer for the major definitions of the performance-based diamond cut grade system.

Angular Spectrum Evaluation Tool ( ASET ): A device that color-codes the angular ranges from which a diamond draws or gathers light.

Angular Spectrum Software Evaluation Tool ( ASSET ): The AGS software program used to establish a diamond cut grade.

Brightness: The amount of white light in a diamond returned to the observer. It is an essential factor in the AGS Laboratories' Diamond Cut Grade analysis.

Brilliance: A diamond’s brightness with positive contrast effects. It is also an essential factor in the AGS Laboratories' Diamond Cut Grade analysis.

Contrast: The light and dark patterns seen when observing a faceted diamond. It can be positive or negative in its optical effect. Usually caused by, but not limited to, the observer’s head. Like Brightness and Brilliance, it is an essential component of the AGS Laboratories' Diamond Cut Grade analysis.

Culet: The point on the bottom of a diamond’s pavilion. A diamond’s culet may be pointed or it may be blunted with a small facet.

Dispersion: The separation of white light into colors by refraction.

Durability: Resistance to chipping or breaking.

Girdle: The band around the outer circumference or edge of a diamond.

Leakage: Areas that do not return light in a diamond.

Light Performance: An analysis of brightness, dispersion, leakage, and contrast in a diamond.

Polish: The quality of the diamond’s surface and edges.

Symmetry: The exactness of the balance and evenness of the diamond’s shape and facets.

Tilt: The point at which the girdle reflects under the table facet.

Weight Ratio: The millimeter footprint of a diamond versus its weight.

To learn more about the AGS Cut Grading System, view any of the following topics:
The AGS 0-10 Grading System
Diamond Cut Grade
Diamond Color Grade
Diamond Clarity Grade
Research and Technology
Performance Cut Grade System