How to Read an IGI Certificate for a Lab-Grown Diamond

When you are buying a lab-grown diamond, the IGI grading report that comes with it is not a formality - it is documentation of what you are actually purchasing. Every number on that certificate tells you something specific about the stone: how big it is, how clear it is, how well it was cut, and whether it has any quirks you should know about.

The problem is that most buyers glance at the certificate, notice the carat weight and maybe the color grade, and then stop there. That leaves most of the report unread - and some of the most important information is in the sections people skip.

Here is how to read every part of an IGI certificate for a lab-grown diamond, in plain language.

What Is an IGI Certificate?

IGI stands for the International Gemological Institute. Founded in 1975 in Antwerp, Belgium, IGI is one of the largest independent gemological laboratories in the world. It has grading facilities in New York, Los Angeles, Mumbai, Hong Kong, Dubai, Tokyo, and several other cities.

IGI has been grading lab-grown diamonds longer than any other major lab, which makes it the dominant certification body for the lab-grown market. When a retailer sells a certified lab-grown diamond, there is a very good chance that certificate is from IGI.

An IGI certificate (officially called a Laboratory Grown Diamond Grading Report) is an independent third-party assessment. The gemologists who grade the diamond have no financial stake in the sale - they are evaluating the stone objectively against established standards.

The 12 Sections on Every IGI Report - and What They Mean

1. Report Number

This is the unique identifier for your specific diamond. Every IGI report has its own number, and you can type it into the IGI online verification tool at igi.org to confirm the certificate is real and unaltered. Do this before you buy. It takes 30 seconds and eliminates any question about document authenticity.

The report number is also laser-inscribed on the girdle of the diamond itself (more on that below).

2. Shape and Cutting Style

This tells you the physical outline of the diamond (round, oval, cushion, emerald, etc.) and how it was cut (Brilliant, Step, Modified Brilliant). A "Round Brilliant" is the most common combination - a round outline cut with 57 or 58 facets arranged to maximize light return. An "Emerald Cut" is a rectangular shape with step-cut facets that create a different, hall-of-mirrors effect.

Shape affects price significantly. Round brilliants command a premium because more rough material is lost during cutting. Fancy shapes - ovals, pears, cushions, marquises - typically cost 10% to 40% less per carat for the same quality grades.

3. Measurements

Expressed as length x width x depth (in millimeters). For a round diamond, this appears as a range for diameter (e.g., 6.40-6.43mm) x depth (e.g., 3.91mm). For fancy shapes, it is the actual length x width x depth.

Measurements matter because two diamonds with the same carat weight can look very different in size depending on how they are proportioned. A diamond cut with a very deep pavilion hides weight in the belly - it weighs what it weighs, but it looks smaller face-up than a well-cut stone of the same carat weight.

4. Carat Weight

One carat equals 0.2 grams. Carat weight is stated to the second decimal place on IGI reports (e.g., 1.02 ct). It is the most direct measure of the size of the diamond, though not the only one - see Measurements above.

Price per carat jumps at key thresholds (0.50 ct, 0.75 ct, 1.00 ct, 1.50 ct, 2.00 ct). A 0.98ct diamond is essentially the same visual size as a 1.00ct diamond but costs meaningfully less. This is worth knowing.

5. Color Grade

IGI grades diamond color on the GIA scale from D (completely colorless) to Z (light yellow or brown). Most buyers aim for the D-J range. Here is a practical guide:

• D-F (Colorless): No detectable color even under magnification. Paired with any metal.
• G-J (Near-Colorless): Color not visible to the naked eye in most settings. G and H are excellent value. I and J can show a hint of warmth, especially in white gold or platinum settings.
• K-Z: Noticeably warm or yellow. Some buyers choose K-M intentionally for yellow gold settings, where the warmth blends in.

For lab-grown diamonds, D-H is the sweet spot for most buyers. The price difference between a D and an H is significant; the visual difference face-up in a ring is minimal.

6. Clarity Grade

Clarity grades describe the presence, size, and location of internal characteristics (inclusions) and surface characteristics (blemishes). The IGI clarity scale:

• FL (Flawless): No inclusions or blemishes under 10x magnification.
• IF (Internally Flawless): No inclusions; minor blemishes possible.
• VVS1 / VVS2 (Very Very Slightly Included): Inclusions extremely difficult to see under 10x magnification.
• VS1 / VS2 (Very Slightly Included): Inclusions difficult to see under 10x; essentially invisible to the naked eye.
• SI1 / SI2 (Slightly Included): Inclusions visible under 10x magnification; usually not visible to the naked eye (especially SI1).
• I1 / I2 / I3 (Included): Inclusions visible without magnification.

For most buyers, VS1-VS2 or SI1 offers excellent value. The inclusions exist, but they are invisible without a loupe. FL and IF grades are mostly for collectors - you are paying for perfection you literally cannot see.

7. Cut Grade

Cut grade is only assigned to round brilliant diamonds on IGI reports. It is graded Excellent, Very Good, Good, Fair, or Poor. Cut affects how the diamond interacts with light - its brightness, fire (rainbow flashes), and scintillation (sparkle). An Excellent cut in a D color VS1 clarity stone will outsparkle a poorly cut D color IF stone every time.

If you are buying a round brilliant, prioritize cut. Excellent cut is the standard to aim for. Very Good is acceptable but measurably dimmer. Good and below show real, visible differences in how the diamond performs under light.

For fancy shapes, IGI does not assign an overall cut grade - you evaluate proportions and polish/symmetry instead.

8. Polish and Symmetry

Two separate grades, each graded Excellent, Very Good, Good, Fair, or Poor.

Polish describes the smoothness of each facet surface. Poor polish can leave microscopic scratches from the cutting wheel that dull the surface brilliance of the diamond.

Symmetry describes how precisely the facets align with each other. Poor symmetry means facets are misaligned, which redirects light in unintended directions and reduces sparkle.

For round brilliants, aim for Excellent/Excellent or Very Good/Very Good at minimum. For fancy shapes, Excellent or Very Good in both is the target.

9. Fluorescence

Fluorescence describes how the diamond reacts to UV light. It is graded None, Faint, Medium, Strong, or Very Strong, with the color noted (almost always Blue).

Strong blue fluorescence in D-F color grades can make the diamond look hazy in direct sunlight - this is why fluorescence carries a price discount in colorless grades. In G-J color diamonds, medium or faint blue fluorescence can actually improve the apparent color, and carries no penalty. None is the safest choice if you are unsure.

10. Comments

This field notes anything unusual about the stone not captured by the standard grades: surface graining, natural indentations, extra facets, or other characteristics. "Additional graining may be present" is a common comment and is not a concern. "Cloud not shown" can sometimes indicate a hazy area that affects transparency - worth asking about.

11. Clarity Plot Diagram

The plot is a diagram of the diamond with symbols marking the location and type of each inclusion and blemish. It is a map of the internal world of the stone. This is useful for confirming that the diamond you receive matches the certificate - the pattern of inclusions should correspond between the plot and what a jeweler can see under magnification.

12. Laser Inscription and Laboratory Grown Designation

This is the most important field unique to lab-grown diamond reports. IGI certificates for lab-grown diamonds prominently state "Laboratory Grown" on the face of the report. The girdle of the diamond is laser-inscribed with the report number and the words "LAB GROWN" (or similar notation). This inscription is permanent, microscopic, and readable under a standard jeweler loupe.

This labeling is required by the FTC (Federal Trade Commission) and exists to ensure full disclosure throughout the supply chain. If a certificate does not clearly state "Laboratory Grown" for a lab-grown diamond, that is a red flag.

How to Verify Your IGI Report Online

Go to igi.org, look for the Report Verification tool, and enter the report number from the certificate. The database will return the full grading information for that report number. Verify that what appears online matches the paper certificate you have - every grade, every number.

This verification step takes less than a minute and is one of the most important things you can do before completing a diamond purchase.

What Good Looks Like: A Practical Buying Benchmark

For a lab-grown round brilliant diamond, this combination delivers outstanding performance and excellent value:

• Color: G or H
• Clarity: VS1 or VS2
• Cut: Excellent
• Polish: Excellent or Very Good
• Symmetry: Excellent or Very Good
• Fluorescence: None or Faint

This profile gives you a diamond that faces up colorless in normal viewing, has no visible inclusions, and sparkles at its full optical potential. You are not paying for grades you cannot see.

If you want to explore EX3 Diamond IGI-certified lab-grown diamond collection, every stone comes with its complete grading report. You can also use those certificates to build your ideal engagement ring with full confidence in what you are selecting.

Frequently Asked Questions

Is IGI as reliable as GIA for lab-grown diamonds?

IGI has been grading lab-grown diamonds longer than GIA and has processed far more lab-grown reports. Both labs use rigorous independent grading methodology. IGI is the industry standard for lab-grown diamond certification, and its grades are widely trusted by retailers and consumers worldwide.

Can an IGI report be faked?

A report number can be copied onto a fraudulent certificate, which is why online verification at igi.org matters. Matching the online record to the paper certificate and the laser inscription on the diamond eliminates this risk.

Does the IGI report tell me if a diamond is lab-grown or mined?

Yes, clearly. IGI reports for lab-grown diamonds state "Laboratory Grown Diamond" on the face of the document, and the laser inscription on the diamond itself includes "LAB GROWN." There is no ambiguity.

What does graining mean in the Comments section?

Graining refers to irregular crystal growth patterns within the diamond. Surface graining appears as faint lines or waves on facets. It is a natural byproduct of the crystal growth process and generally has no visible impact on the appearance of the diamond at normal viewing distances.

Should I buy a diamond without a certificate?

No. Without an independent grading report, you have only the word of the seller for the quality of the stone. An IGI certificate is proof of what you are buying, not an optional extra. Every lab-grown diamond from EX3 Diamond comes with full IGI documentation.

What is the difference between a certificate and an appraisal?

A grading certificate (like an IGI report) describes the physical characteristics of the diamond objectively. An appraisal assigns a dollar value to the stone, typically for insurance purposes. They serve different functions - you need the certificate to understand what the diamond is, and an appraisal to establish replacement value for insurance.

The Bottom Line

An IGI certificate is a precise technical document, but it is readable with a little context. Once you know what each section means, you can evaluate any lab-grown diamond with confidence - color, clarity, cut, and all the details that determine what you are actually buying.

The key habits: read past the carat weight, verify the report number online, check that the certificate clearly states "Laboratory Grown," and match the clarity plot to what is in the stone. Do those four things, and no one is going to sell you something other than what is on the page.

EX3 Diamond: Responsible. Traceable. Scintillating.