The International Gemological Institute (IGI) is now issuing cut grades for loose fancy shape diamonds.
IGI’s reports for fancy shapes will still feature its standard polish and symmetry analysis, but will also include a grade assessing how cut quality influences the light behavior seen in fancy shapes. The cut grade will be offered at IGI’s 20 worldwide laboratories and will be optional for manufacturers for the next six months.
“Fancy shapes are more complex than round brilliants,” says IGI’s senior director of education, John Pollard. “The performance of a round can be predicted decisively if you know its performance. But with fancy shapes, you can’t predict light performance with proportions.”
Because of this, the IGI has developed a four-step system—explained here—that combines proportion requirements with visual assessment.
The first step uses IGI’s traditional grades for polish and symmetry. Fancy shape diamonds that receive very good or excellent on polish and symmetry become candidates for an overall excellent cut grade.
The second step involves proportions. “We can provide producers with a range of proportion qualifications that have been historically observed to provide the most positive beauty components,” Pollard says.
The third step involves shape-specific requirements, such as a bow tie on an oval, marquise, and pear. In the princess, the chevrons in the pavilion must be even. Pears must have a rounded base and even shoulder.
Finally, there’s “light return grading.”
“This is not an assessment of fire or scintillation,” Pollard says. “It is an evaluation of fundamental light behavior, determining whether the diamond returns sufficient light to the viewer to be considered top of class or excellent for that shape.”
IGI is currently providing its “Guidelines for Excellent” to all producers.
For now, every diamond grading lab seems to be handling grading fancy shapes in different ways.