An IGI report — formally a grading document issued by the International Gemological Institute (IGI) — is one of the most widely encountered laboratory certificates in the global diamond and gemstone trade. Founded in Antwerp in 1975, IGI operates grading laboratories across Europe, Asia, and North America, and has grown into one of the largest independent gemmological laboratories by volume of reports issued. Its certificates cover polished diamonds, coloured gemstones, and finished jewellery, and are recognised by trade buyers and retail consumers in most major markets.

Diamond Grading Reports

The core IGI product is its polished-diamond grading report, which assesses the four principal quality factors — carat weight, colour, clarity, and cut — using methodology broadly aligned with international gemmological standards. A standard IGI diamond report includes:

• Precise carat weight to the nearest hundredth of a carat
• Colour grade on the D-to-Z scale
• Clarity grade from Flawless to I3, with a plotted diagram of inclusions
• Cut grade (Excellent through Poor) for round brilliants, encompassing proportions, symmetry, and polish
• Fluorescence description (None, Faint, Medium, Strong, Very Strong)
• Table and depth percentages, crown and pavilion angles, and girdle thickness
• A unique report number, often laser-inscribed on the girdle of the stone

IGI also issues reports for fancy-shaped diamonds and, increasingly, for laboratory-grown diamonds — a segment in which the laboratory has become particularly prominent, given the rapid expansion of the lab-grown market in India, the United States, and elsewhere.

Coloured Gemstone and Jewellery Reports

Beyond diamonds, IGI offers identification and quality reports for coloured gemstones, assessing species, variety, geographic origin (on selected reports), and the presence of treatments such as heat, fracture filling, or beryllium diffusion. The laboratory also issues appraisal-style reports for finished jewellery pieces, which are used primarily in retail and insurance contexts rather than in high-end auction or wholesale trade.

Market Position and Trade Perception

IGI occupies a distinct position in the grading-laboratory hierarchy. In the high-value polished-diamond segment — particularly for stones above one carat — GIA (Gemological Institute of America) remains the benchmark laboratory in most Western auction and wholesale markets, and price premiums are routinely attached to GIA-graded stones. IGI reports are, however, widely accepted in retail jewellery markets across Europe, South and South-East Asia, and the Middle East, where the laboratory's physical presence and turnaround times make it a practical choice for trade clients.

For laboratory-grown diamonds, IGI has established a particularly strong foothold, and its grading of lab-grown stones is broadly accepted across the trade. The laboratory's acquisition by a major diamond industry group in 2023 prompted some discussion within the trade regarding independence, though IGI has maintained that its grading standards and laboratory operations remain separate from commercial interests.

Interpreting an IGI Report

When evaluating an IGI-graded stone, buyers and gemmologists should bear in mind several practical considerations. Grading consistency across laboratories is an acknowledged industry challenge: independent studies and trade experience have noted that IGI grades — particularly for colour and clarity — have at times been assessed as slightly more generous than equivalent GIA grades on the same stones, though this varies by period and by the specific laboratory facility. For significant purchases, cross-referencing with a GIA or other major laboratory report, or commissioning an independent appraisal, remains advisable. The report number should always be verified against IGI's online verification portal to confirm authenticity.

Further Reading

• International Gemological Institute — igi.org
• GIA: Laboratory-Grown Diamonds — gia.edu