Understanding Every Line on Your Diamond Report
The IGI (International Gemological Institute) diamond grading report is the official document that verifies your diamond's characteristics. It is created by independent gemologists who examine your diamond using standardized methods and equipment. Here is how to read every section of your report.
Report Number
- What it is: A unique identification number assigned to your specific diamond. No two diamonds share a report number
- Laser inscription: This number is typically laser-inscribed on the diamond's girdle (the thin edge around the widest point). It is invisible to the naked eye but visible under 10x magnification
- Verification: You can verify any IGI report number on the IGI website. Enter the number and the report data should match your physical report exactly
Shape and Cutting Style
- What it tells you: The diamond's shape (Round Brilliant, Oval Modified Brilliant, Emerald Step Cut, etc.) and the faceting style used
- Why it matters: Confirms you are getting the shape you ordered. Also helps you understand the light performance expectations for your specific diamond shape
Measurements
- What it tells you: The exact dimensions of the diamond in millimeters. For round diamonds: minimum diameter - maximum diameter x depth. For fancy shapes: length x width x depth
- Why it matters: Measurements tell you the actual size of the diamond — how large it appears face-up. Two diamonds with the same carat weight can have different measurements due to different depth proportions
The 4Cs
- Carat weight: The precise weight of the diamond to the hundredth of a carat. A 1.05 ct diamond is exactly 1.05 carats — 210 milligrams
- Color grade: The body color of the diamond on the D-Z scale. D is completely colorless. Z has a noticeable tint. G-H is the sweet spot for most buyers
- Clarity grade: The presence of inclusions and blemishes. FL (flawless) to I3 (heavily included). VS2 is the recommended sweet spot — eye-clean with no visible imperfections
- Cut grade: For round brilliants: Excellent, Very Good, Good, Fair, Poor. The cut grade reflects proportions, symmetry, and polish. ALWAYS choose Excellent
Proportions
- Table percentage: The width of the top flat facet relative to the total width. Ideal for round: 54-58%
- Depth percentage: The total height relative to the total width. Ideal for round: 59-62.5%
- Crown angle: The angle of the crown facets. Ideal: 34-35 degrees
- Pavilion angle: The angle of the bottom facets. Ideal: 40.6-41.0 degrees
- These proportions determine light performance: Even without understanding the numbers, if the cut grade is Excellent, the proportions are already optimized
Additional Grading Data
- Polish: The smoothness of the facet surfaces. Excellent is ideal
- Symmetry: How well-aligned the facets are. Excellent is ideal
- Fluorescence: None, Faint, Medium, Strong, or Very Strong. Blue fluorescence in G-J colors can actually improve appearance
Inclusion Plot
- A diagram showing the type and approximate location of inclusions inside the diamond
- Useful for understanding where inclusions are positioned — inclusions near the edges are less visible than inclusions in the center