How cut is graded

A diamond's cut grade generally covers three things: proportions, polish and symmetry. Grading standards differ from one authority to another. China's national standard grades cut as Very Good, Good or Fair. Among the major international gem laboratories, GIA grades cut as Excellent, Very Good, Good, Fair or Poor, while IGI's top grade is Ideal, followed by Excellent and on down.

Choosing an ideal cut

A good cut shows a diamond at its most brilliant, with proportions that reflect light as close to perfectly as possible. A diamond's cut is not summed up by a single EX or VG; it combines the grades for proportions, polish and symmetry. The top grade on a GIA report, 3EX, means all three are graded Excellent.

For a GIA report, use the standards below. For other laboratories, adjust according to the relative importance of the three.

  1. First choice Cut EX, polish EX, symmetry EX
  2. Second choice Cut EX, polish VG, symmetry EX
  3. Minimum Cut VG, polish VG, symmetry VG