CDG Case Analysis & Practical Application 3

Question 1

A round brilliant diamond has a table percentage of 72% and a crown angle of 25 degrees. How does this combination most likely affect light performance?

Accepted Answer

The large table combined with a flat crown reduces fire and may create a 'fisheye' effect

Answer

A very large table percentage combined with a shallow crown angle reduces the crown's ability to disperse light, diminishing fire and risking a fisheye reflection of the girdle.

Question 2

A diamond grader measures a pavilion angle of 41.5 degrees. What light performance issue is most associated with this steep pavilion?

Accepted Answer

A dark 'nail head' appearance in the center of the stone face-up

Answer

A pavilion angle above approximately 41 degrees causes light to reflect back at a steep angle, creating a dark central zone known as a 'nail head' effect when viewed face-up.

Question 3

A grader assigning a Polish grade observes minor abrasions on several facet edges but no scratches or nicks. What Polish grade is most appropriate?

Accepted Answer

Good

Answer

Minor abrasions visible under 10x but not individually severe typically place the polish grade at Good rather than Very Good or Excellent.

Question 4

When assigning a Symmetry grade, you discover the culet is noticeably off-center from the table. Which symmetry grade is most appropriate if this is the only deviation observed?

Accepted Answer

Good or Fair, because an off-center culet is a significant symmetry deviation

Answer

An off-center culet is a significant symmetry characteristic that, even alone, typically lowers the symmetry grade to Good or Fair depending on severity.

Question 5

A cutter has produced a round brilliant with a 34-degree crown angle and a 40.75-degree pavilion angle. How would GIA most likely grade the overall cut?

Accepted Answer

Excellent or Very Good, as this combination falls within the optimal range for light performance

Answer

A crown angle of 34 degrees paired with a pavilion angle of 40.75 degrees falls within GIA's well-documented optimal range for achieving Excellent to Very Good cut grades.

(CDG) Certified Diamond Grader Practice Test

(CDG) Certified Diamond Grader Practice Test

CDG Case Analysis & Practical Application 3