Introduction
The International Gemological Institute is the largest diamond grading laboratory in the world by volume. That single fact shapes everything else about IGI — its strengths, its market position, and the questions buyers should ask when they encounter an IGI report.
Founded in Antwerp in 1975, IGI built its business on scale and accessibility. While GIA defined the grading system and HRD embedded itself in the Antwerp trade, IGI expanded aggressively across continents, opening laboratories in every major diamond cutting and trading centre. When the lab-grown diamond market began its rapid growth, IGI was positioned to grade the volume — and it did. Today, the vast majority of lab-grown diamonds reaching consumers carry IGI reports.
For Czech buyers, IGI is the laboratory you are most likely to encounter on lab-grown diamonds and on some natural diamonds in the mid-market segment. Understanding what IGI does well, where its grading calibration differs from GIA's, and how to interpret its reports is essential for making informed comparisons.
Key Points
Founding and Growth
IGI was established in 1975 in Antwerp, Belgium — the same city that hosts GIA's European laboratory and HRD Antwerp's headquarters. The diamond district in Antwerp was the logical starting point for any new grading operation, and IGI initially served the local trade with grading and identification services.
What distinguished IGI from its competitors was its growth strategy. Rather than concentrating operations in a few major centres, IGI pursued a decentralised model, opening laboratories across the globe. Today, IGI operates facilities in Antwerp, New York, Mumbai, Surat, Hong Kong, Shanghai, Dubai, Tel Aviv, and other locations — a network that spans every major diamond market. This geographic reach gives IGI logistical advantages: diamonds can be submitted for grading close to where they are cut, reducing transit time and cost.
The scale is substantial. IGI processes more grading reports than any other laboratory. This throughput is driven partly by its natural diamond work but primarily by its dominant position in the lab-grown diamond market, where volume is high and turnaround speed matters to producers and retailers.
Ownership and Corporate Changes
IGI's corporate history diverges from GIA's non-profit model. IGI has always been a commercial entity, and its ownership has changed hands several times. The most significant recent development was the acquisition of a majority stake by Blackstone, the American private equity firm, in 2023. Blackstone's investment signalled institutional confidence in IGI's growth trajectory — particularly its lab-grown diamond business — and brought the kind of capital and corporate infrastructure associated with large-scale commercial expansion.
Following the Blackstone acquisition, IGI pursued a public listing on the Indian stock exchanges in late 2024, reflecting the importance of India's diamond cutting industry to IGI's operations.
For buyers, the practical question is whether commercial ownership creates incentives that differ from a non-profit structure like GIA's. The concern is straightforward: a for-profit laboratory that depends on grading fees has a structural incentive to attract submissions, and generous grading is one way to do that. IGI maintains internal quality controls and grading protocols to guard against this, but the structural incentive exists in a way it does not at GIA. This is worth understanding without overstating — IGI is a legitimate, internationally recognised laboratory. But the ownership model is part of the context.
Lab-Grown Diamond Grading
IGI's defining market position is its dominance in lab-grown diamond grading. When the lab-grown segment began scaling commercially in the mid-2010s, IGI invested early and heavily in grading capacity for these stones. The result is that today, the overwhelming majority of lab-grown diamonds sold globally carry IGI reports.
This dominance is not accidental. Lab-grown diamond production generates high volume at lower per-stone values compared to natural diamonds. Producers need a grading laboratory that can handle large quantities with fast turnaround at competitive pricing. IGI's global laboratory network and throughput capacity made it the natural fit. GIA, which introduced its own lab-grown diamond grading report later and at a more measured pace, holds a smaller share of this market.
For Czech consumers shopping for lab-grown diamonds, an IGI report is the standard you will encounter. It provides the same 4Cs assessment framework — colour, clarity, cut grade, and carat weight — applied to lab-grown stones, along with a clear identification that the diamond is laboratory-grown. See Report vs Certificate for what a grading document represents, and Natural vs Lab-Grown Overview for the broader comparison between natural and lab-grown diamonds.
Natural Diamond Grading: The Calibration Question
This is where buyers need to pay attention. IGI grades natural diamonds using the same 4Cs framework originated by GIA — the D-to-Z colour scale, the Flawless-to-Included clarity scale, and the standard cut grade terminology. See Normal Colour Range and GIA Clarity Scale for the scales themselves.
However, the trade's longstanding observation — consistent across dealers, gemologists, and pricing professionals — is that IGI's natural diamond grades tend to run more generous than GIA's. The pattern is most visible on colour and clarity:
Colour. An IGI colour grade may sit one grade, occasionally two grades, above what GIA would assign to the same stone. A diamond graded F by IGI might receive a G or even H from GIA. This is not a universal rule — some stones will receive identical grades from both laboratories — but the tendency is well-documented in trade experience.
Clarity. Similar patterns appear on clarity, though less consistently. A VS2 from IGI may correspond to an SI1 at GIA on some stones. The discrepancy is most common at grade boundaries where human judgment plays the largest role.
Cut. Cut grade differences between IGI and GIA are less discussed, partly because cut grading involves more objective proportion measurements. Differences exist but are narrower than on colour and clarity.
Why does this matter? Because diamond pricing is grade-dependent. A diamond listed as G colour VS2 at a certain price is only a fair deal if the grades are reliable. If the stone's colour is actually closer to H and its clarity closer to SI1 by GIA standards, the market price should be lower. A buyer who compares an IGI-graded diamond against a GIA-graded diamond of the same stated grades without adjusting for calibration differences may overpay.
This does not make IGI reports worthless — it means they need to be read in context. See Why Grading Differs Between Labs for a detailed treatment of inter-laboratory variation and its pricing implications.
Report Types
IGI issues several types of grading documents:
IGI Diamond Report. The full grading report for natural and lab-grown diamonds, including 4Cs grades, measurements, proportions, fluorescence, and a clarity plot. Comparable in scope to the GIA Diamond Grading Report.
IGI Diamond Identification Report. A compact document confirming the diamond's identity (natural or lab-grown) with basic characteristics, without full 4Cs grading.
IGI Hearts and Arrows Report. A specialised report for round brilliants that demonstrate the hearts-and-arrows optical pattern, including images of the pattern. See Hearts and Arrows for what this pattern indicates about cut precision.
IGI Jewellery Report. Evaluates finished jewellery pieces, including mounted diamonds and the metal setting. Similar to HRD's jewellery grading service.
All IGI reports include a unique report number and can be verified through IGI's online verification portal. See Online Report Verification for the process.
IGI and the Czech Market
Czech consumers encounter IGI reports in two primary contexts: lab-grown diamonds purchased from international retailers, and natural diamonds in the mid-market segment sourced through dealers who use IGI grading.
For lab-grown diamond purchases, an IGI report is appropriate and expected. It is the market standard, and buyers can rely on it for identification and basic quality assessment. The grading calibration questions that apply to natural diamonds are less commercially significant for lab-grown stones, where price points are lower and resale value is not a primary consideration.
For natural diamond purchases, apply more caution. If you are comparing an IGI-graded natural diamond against a GIA-graded stone, do not treat identical grades as identical quality. Either request that both stones be evaluated by the same laboratory, or adjust your price expectations to account for potential grading differences. For natural diamonds above approximately 30 000 CZK, a GIA or HRD Antwerp report provides a more conservative and widely benchmarked grading standard.
At Arete Diamond, we primarily use GIA reports for natural diamonds. When we offer IGI-graded stones — typically in the lab-grown category — we ensure the grading context is clearly communicated so buyers can make informed comparisons.
Summary
IGI is the world's largest gemological laboratory by grading volume, with a global network of facilities spanning every major diamond market. Founded in Antwerp in 1975 and now backed by Blackstone's investment, IGI has grown through scale, geographic reach, and early dominance in the lab-grown diamond segment. For lab-grown diamonds, IGI is the industry standard — its reports are appropriate, widely accepted, and expected. For natural diamonds, IGI's grading calibration tends to be more generous than GIA's, particularly on colour and clarity. This does not disqualify IGI reports, but it means buyers must account for the difference when comparing stones and evaluating prices. Read IGI grades as one expert's assessment, compare them within their own context, and verify every report online before purchasing.