Learning the Language of Performance
The AGS Light Performance Cut Grade System added new terms to the lexicon of the diamond industry. Below is a primer of words and terminology applicable to this revolutionary 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 cut grade.

Brightness: The amount of white light returned to the observer.

Brilliance: Brightness with positive contrast effects.

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.

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

Durability: Resistance to chipping or breaking.

Leakage: Areas that do not return light.

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

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

Tilt: The point at which the girdle reflects in the table and is defined by the minimum pavilion angle allowed for each table size.