1. Round Brilliant Cut Diamonds
Assessments: Polish, Symmetry, Proportions and Light Performance
IGI assesses round brilliant cut diamonds in the areas of polish, symmetry, and proportions (finish). The top cut grade a round brilliant diamond can earn is Excellent-Ideal.
Light Performance Report
Diamonds of the same shape can have different visual tendencies. For this reason IGI issues a light performance report for round diamonds which display top optical performance, providing an easily understood breakdown of their quantifiable beauty components.
- Total Light Performance: Cumulative intensity of the diamond’s brightness, fire, contrast and scintillation.
- Brightness: All reflected and refracted white light
- Fire*: Dispersed light seen as flashes of color
- Contrast: Balance and intensity of bright and dark areas
The Ideal-Scope Representation, generated with ray-tracing software, conforms to the diamond’s specific parametric averages, permitting further verification and analysis of its fundamental light behavior in the Ideal-Scope, a scientific light performance assessment tool.
Round Brilliant Methodology
IGI researchers used ray-tracing software to analyze light performance for round brilliant diamonds spanning thousands of proportions sets and 18 table sizes. Parameters judged to have Exceptional performance, overall, were isolated and further assessed to arrive at four summary calculations: Total Light Performance, Brightness, Fire* and Contrast.
*Fire is only seen in conducive lighting
Video overview: Light Performance Grading
2. Fancy Shaped Diamonds
Assessments: Polish, Symmetry, Craftsmanship and Light Return
Fancy Shape Methodology
IGI grades the cut of fancy shaped diamonds on a scale ranging from Excellent to Poor, assessing polish, symmetry, proportions, and additional craftsmanship requirements in a four-step process.
- Polish and symmetry grading
- Proportions qualification
- Additional craftsmanship requirements
- Light return grading
Video overview: Fancy Shape Cut Grading
Fancy Shape Cut Grading: Four Step Process
Step 1: Polish and symmetry grading
- Diamonds earning a minimum of Very Good in both areas become candidates for an overall cut grade of Excellent
Step 2: Proportions qualification
- Fancy shape cut quality cannot be graded using proportions (alone) but IGI has published parameters historically observed to produce the most positive beauty components in different shapes
- Diamonds within those parameters remain candidates for Excellent
Step 3: Additional craftsmanship requirements
- Shape specific requirements designed to analyze bow-ties, girdle ranges and other factors which vary by shape
- Diamonds meeting these requirements remain candidates for Excellent
Step 4: Light return grading
- As with color, clarity and finish grading, this assessment is performed by a trained gemologist
- This is not an assessment of fire or scintillation. It is an evaluation of fundamental light behavior, determining whether the diamond returns sufficient light, overall, to be considered top of class, or Excellent, for that shape
- Fancy shaped diamonds which successfully pass the first three steps and have Excellent light return will receive the overall cut grade of Excellent