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New AGS Cut Grading System - useful definitions

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starryeyed

Ideal_Rock
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Nov 6, 2006
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Hi Gang. I thought this might be a useful reference: (from AGS)

There are three categories in the new AGS Cut Grading System — Light Performance, Proportions, and Finish. Within these categories are eleven factors:

Light Performance: Brightness, Dispersion, Leakage, Contrast
Proportions: Durability, Tilt, Weight Ratio, Girdle Thickness, Culet Size
Finish: Polish, Symmetry

DEFINITIONS:

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 diamond. It can produce a positive or negative optical effect. This usually is caused by, but not limited to, the observer’s head.
Dispersion: The separation of white light into spectral colors.
Durability: The diamond’s resistance to chipping or breaking.
Leakage: Areas that do not return light.
Scintillation: The combination of white and colored sparkles seen as the diamond and/or the observer and/or the light source(s) move.
Tilt: The point at which the girdle reflects under the table of the diamond and is defined by the minimum pavilion angle allowed for each table size.
Weight Ratio: The millimeter footprint of a diamond versus its weight.

The AGS Performance Grading Software objectively measures and evaluates nine of the eleven grading factors. The remaining two — Polish and Symmetry — must be evaluated by a diamond grader.

The AGS ASET provides a quick and easy — yet sophisticated — way to assess a diamond’s interaction with light. The name ASET stands for Angular Spectrum Evaluation Tool, and the device was developed to be used with the performance-based American Gem Society Diamond Cut Grading System.

from: www.americangemsociety.org
 
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