The Gemological Institute of America (GIA) grades the cut of a diamond as either:
- Excellent (the best grade)
- Very Good
- Poor (the worst grade)
Below are the details that will help you understand GIA’s diamond cut grading system, and what distinguishes an “excellent” from a “good” or “fair” cut.
Excellent Grade (EX)
Excellent Grade has high brilliance, scintillation and an even pattern of light and dark areas.
Very Good Grade (VG)
This grade also has high brilliance and scintillation, but expect them to be a bit darker in the center or around the edges. In some cases a diamond can have top brilliance and scintillation, but be down graded by its pattern. The stone above has a splintery pattern that prevents it from being graded excellent.
Good Grade (G)
This grade will be generally be a bit darker or lacking in scintillation. The stone above is dark around its girdle. A stone can also be downgraded by its pattern, or its weight ratio. I.E. if it weighs more than an average gem of this diameter, it will be downgraded one step.
Fair Grade (F)
A gem in this category will have very little brilliance or scintillation. The stone…