The AGS Ideal Report by GIA is a digital supplement to a GIA report. It gives the American Gem Society's light performance grade, and only AGS Ideal 0 stones get one.
In more detail
A round must first be a GIA "Triple Excellent": Excellent cut, polish and symmetry, in the D-to-Z range. Some facet designs of the cushion, oval, emerald, radiant, princess and fancy round also qualify. They need Excellent polish and symmetry. Marquises and pears are not on the list, and the report comes with or without an ASET map.
On a grading report
A separate supplement, not a line on the main report. On GIA paperwork, "Ideal" appears only here, never as a cut grade.
Related terms
- Ideal cut: "Ideal cut" has three meanings: an IGI comment, a GIA supplement grade, or a sales word. At IGI it marks an Excellent round with narrower proportions; at GIA it appears only as "AGS Ideal".
- Triple Excellent: Triple Excellent is trade shorthand for a GIA round brilliant with Excellent cut, Excellent polish and Excellent symmetry.
- ASET map: An ASET map is a four-color picture that shows from which directions a stone's face-up light comes. It can be part of the AGS Ideal Report by GIA.
- Cut grade: The cut grade rates how well a diamond's proportions and finish work, from Excellent to Poor. GIA gives it only to standard round brilliants in the D-to-Z color range.
- Light performance: Light performance is how well a cut stone handles light. We describe it with brilliance (light returned), fire (color) and scintillation (sparkle).