Reading Your Diamond's Report Card
Every IGI certified diamond comes with a detailed grading report that documents the diamond's exact characteristics. Understanding how to read this report empowers you to verify quality, compare diamonds accurately, and make confident purchasing decisions. Here is what every section of an IGI report means.
Report Header
- Report number: A unique identification number. You can verify any IGI report at igi.org by entering this number
- Report date: When the diamond was graded. Reports do not expire — a diamond's characteristics do not change over time
- Report type: Natural diamond report or laboratory grown diamond report. IGI clearly identifies the origin
Shape and Cutting Style
This section identifies the diamond's shape (round, oval, cushion, etc.) and its faceting style (brilliant, step, modified brilliant, or mixed). Most popular shapes are brilliant cut, which maximizes sparkle through triangular and kite-shaped facets.
Measurements
- For round diamonds: Minimum diameter - Maximum diameter x Depth (e.g., 6.50 - 6.53 x 4.02 mm)
- For fancy shapes: Length x Width x Depth
- These measurements determine the diamond's proportions and help verify carat weight accuracy
The 4Cs Grades
- Carat Weight: Measured to the hundredth of a carat (e.g., 1.52 ct). This is the diamond's actual weight, not an approximation
- Color Grade: D (colorless) through Z (light yellow/brown). D-F are colorless, G-J are near-colorless, K+ shows visible color
- Clarity Grade: FL through I3. Indicates the visibility of inclusions under 10x magnification
- Cut Grade (round only): Excellent, Very Good, Good, Fair, Poor. Based on proportions, symmetry, and light performance
Proportions Diagram
A cross-section diagram showing the diamond's exact proportions as percentages of diameter. Key measurements include table percentage (top flat facet width), depth percentage (total depth), crown angle, pavilion angle, star length, and lower half length. For round diamonds, ideal proportions are well-established and directly correlate with sparkle.
Additional Grading
- Polish: Quality of the diamond's surface finish. Excellent to Poor
- Symmetry: How precisely the facets are aligned and shaped. Excellent to Poor
- Fluorescence: None, Faint, Medium, Strong, Very Strong. Indicates the diamond's reaction to UV light
Why IGI Certification Matters
An IGI report is an independent, objective assessment by trained gemologists using standardized criteria and equipment. It protects the buyer by verifying that the diamond matches its seller's claims. Without a reputable grading report, you are relying entirely on the seller's word.