The International Gemological Institute (IGI) was founded in 1975 in Antwerp, Belgium — the historic center of the global diamond trade. Today, IGI operates laboratories on every inhabited continent and has become the world's largest independent gemological organization by volume. IGI is particularly notable as the leading certifier of lab-grown diamonds.
IGI's Role in the Lab-Grown Market
While GIA and AGS have historically focused on natural diamonds, IGI recognized the lab-grown diamond market early and positioned itself as the go-to certifier. Today, the vast majority of lab-grown diamonds sold by major retailers carry IGI certification. This specialization has given IGI deep expertise in grading lab-grown stones and identifying their growth methods.
IGI grades lab-grown diamonds using the same 4Cs framework applied to natural diamonds, with reports that clearly identify the stone as laboratory-grown and note the creation method (HPHT or CVD) when determinable.
IGI Grading Standards
IGI uses grading scales that align with industry standards:
Cut: Ideal, Excellent, Very Good, Good, Fair. IGI's inclusion of an "Ideal" grade above "Excellent" is similar to AGS's approach, providing a higher tier for exceptional cut quality.
Color: D through Z scale, consistent with GIA's system.
Clarity: FL through I3, using the same grades as GIA.
IGI vs. GIA Grading Consistency
It is generally acknowledged in the industry that IGI's grading can be slightly more lenient than GIA's, particularly for color and clarity of natural diamonds. A diamond graded G color by IGI might receive an H color grade from GIA. This difference is typically one grade at most, but it can affect pricing.
For lab-grown diamonds, IGI's grading consistency is considered strong because they have the most experience and volume in this specific area. If you are purchasing a lab-grown diamond with IGI certification, you can be confident in the report's accuracy.
For natural diamonds, if both a GIA and IGI certificate are available at a similar price, the GIA certificate is generally preferred for its stricter standards and wider industry recognition. However, an IGI-certified natural diamond from a reputable seller is still a trustworthy purchase.
IGI Report Features
IGI reports include detailed information on the 4Cs, proportions, fluorescence, and a clarity plot for larger diamonds. Reports can be verified online at IGI's website (igi.org) using the report number. IGI also offers laser inscription services for linking a physical diamond to its report.
When to Choose IGI
IGI certification is an excellent choice when purchasing lab-grown diamonds — it is the industry standard in that space. For natural diamonds, IGI is a credible option, especially for diamonds purchased from reputable retailers. However, for high-value natural diamonds (over $5,000), a GIA or AGS certificate provides additional peace of mind due to their slightly stricter grading standards.