Case Analysis & Practical Application Flashcards

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?

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

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.

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

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

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.

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

Answer: Good

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

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?

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

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

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?

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

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.

You are grading a round brilliant with a girdle that grades as Thick to Very Thick. What is the most significant concern this raises beyond the girdle grade itself?

Answer: The extra weight in the girdle increases carat weight without contributing to face-up size, reducing value per carat

A very thick girdle hides excess weight that does not contribute to face-up diameter, meaning the stone appears smaller than its carat weight would suggest, reducing value per carat.

A diamond has 65 facets instead of the standard 58 due to extra facets on the pavilion. How do extra facets affect the GIA cut grade?

Answer: Extra facets are noted as a symmetry characteristic and can lower the symmetry grade if they are asymmetrical

Extra facets are a symmetry characteristic; if they are asymmetrically placed or visually disruptive, they are noted on the report and may lower the symmetry grade.