The International Gemmological Institute, almost universally referred to as IGI, is one of the largest gemmological laboratory networks in the world. Founded in Antwerp in 1975, IGI operates laboratories and educational facilities in roughly 30 cities including New York, Mumbai, Bangkok, Hong Kong, Tokyo, Toronto, Dubai, Tel Aviv and Shanghai. It issues grading reports and identification certificates for diamonds, coloured stones, laboratory-grown diamonds and finished jewellery, and runs gemmology and jewellery design courses through its IGI School of Gemology.

Foundation and growth

IGI was founded in 1975 in Antwerp at a time when the Belgian city was the centre of the global rough-diamond trade. The original mandate was diamond grading for the Antwerp market, and the laboratory built its early reputation on diamonds. Over the following decades IGI expanded geographically, first into the United States with the New York office, then into Asia, where the rapid growth of cutting industries in India and Thailand created demand for local certification. The Mumbai laboratory has become particularly large and serves as the principal certifying authority for a substantial share of polished diamond output from Surat and the surrounding cutting centres.

Diamond grading

IGI grades natural diamonds against the same 4Cs framework used industry-wide. Reports include carat weight, colour, clarity and cut grade, alongside fluorescence, polish, symmetry and proportions. The laboratory plots inclusions on a diagram, and full laser-inscribed reports tie a unique identification number to the stone's girdle. IGI's grading scales correspond to those used by GIA and other major laboratories, although in some borderline cases the trade has historically observed slight differences in grade calls between the laboratories. For this reason, the trade's choice of laboratory often follows the destination market's expectations rather than a single global standard.

Laboratory-grown diamond reports

IGI was an early adopter of dedicated grading reports for laboratory-grown diamonds, and the laboratory now grades a large proportion of the world's lab-grown stones. Reports clearly identify a diamond as laboratory grown, distinguish CVD from HPHT growth where determinable, and disclose post-growth treatments such as HPHT colour modification or annealing. The 2020s expansion of the lab-grown segment has made IGI's lab-grown reports a standard reference in the trade.

Coloured-stone identification and grading

IGI's coloured-stone work covers identification, treatment determination and origin opinions for the major species. Reports identify the stone, list any treatments detected (heat, oil, glass filling, diffusion, irradiation) and, on request, give a country-of-origin opinion for ruby, sapphire, emerald, Paraiba tourmaline and a small number of other species. IGI also issues coloured-stone grading reports against its internal scale, although the AGL, Gübelin, SSEF and Lotus laboratories remain the most cited references at the high end of the coloured-stone market.

Education

The IGI School of Gemology offers diploma and short courses in Antwerp, Mumbai, Bangkok, New York, Toronto and several other locations. The curriculum covers diamond grading, coloured-stone identification, jewellery design and laboratory technique. The diplomas are recognised in the international trade alongside the GIA, FGA and other major credentials, although hiring laboratories and dealers in different markets weight them differently.

Trade position

In market terms IGI is one of the four or five laboratories whose reports trade routinely throughout the world, alongside GIA, HRD, AGS and the European laboratories. The choice between them in any given transaction is driven by location, by buyer preference and by the specific service required, particularly for laboratory-grown diamonds, where IGI's volume gives it a leading practical position.