IGI vs GIA vs GCAL for Lab Grown Diamonds

Three names appear on almost every lab grown diamond report: IGI, GIA, and GCAL. They are not interchangeable, and in lab grown they do not compete for the same job. One dominates volume, one is retreating from granular grading, and one sells precision and a guarantee.

IGI, the International Gemological Institute, is the volume leader. Its managing director and chief executive Tehmasp Printer put IGI's share at roughly 65 percent of global lab grown diamond certification and 33 percent of the overall diamond certification market, growth the company tied directly to synthetic diamond demand.¹ IGI applies the full traditional D to Z colour scale and FL to I3 clarity scale to every lab grown stone it grades, with no tier compression.⁵

GIA, the Gemological Institute of America, is the historical authority for natural diamonds and a minor player in lab grown volume. GIA has stated it grades fewer than 5 percent of lab grown diamonds.² Together, GIA and IGI account for roughly 80 percent of the overall certification market, which analysts project to reach 1 billion US dollars by 2028, driven by lab grown.⁶

GCAL, the Gem Certification and Assurance Lab, is a boutique. It does not publish a mass market volume share. Its position is consumer protection and cut precision, anchored by the GCAL 8X report and a written guarantee described below.³

For lab grown diamonds, IGI is the market standard and the practical default. It grades the majority of lab grown stones and retains the full granular scales. The nuance buyers hear about is grading strictness, and it deserves a careful, neutral answer.

Trade and retailer education sources consistently report that GIA has historically graded more conservatively, and that IGI placements can run one to two increments higher on the same stone. One worked example: a stone graded VS1 by GIA might read VVS2 at IGI.⁷ A second, in the other direction of measurement: a stone graded VS1 and G by IGI might read VS2 and H at GIA, one step lower on both colour and clarity.⁵ The framing across sources is a gap of roughly one to two grades of colour or clarity on comparable stones.

Read this correctly. The difference is one of scale and reference sample, not reliability. IGI grades rigorously against the same D to Z and FL to I3 scales; the reported effect is that its placements can sit a step more generous than GIA's historically conservative bench. That is a documented, third party observation, not a claim that either lab is wrong. It is also worth stating plainly that no blind, peer reviewed cross lab study exists to quantify the gap. The evidence base is trade reporting and repeated worked examples, not a controlled sample. We treat it as a directional tendency, not a fixed number of grades.

There is a structural change that makes the old IGI versus GIA grade comparison largely moot after October 2025. GIA no longer issues D to Z colour or FL to I3 clarity grades for lab grown at all, so a direct grade for grade comparison against IGI is no longer possible for new GIA lab grown reports. Among the three, IGI is now the only lab issuing granular 4Cs grades for lab grown at scale.⁷

Effective October 1 2025, GIA stopped applying the natural diamond 4Cs nomenclature to lab grown diamonds. It replaced specific D to Z colour and FL to I3 clarity grades with a two tier descriptive system: Premium or Standard.⁴ Prior D to Z services for lab grown remained available only through September 30 2025.

The rationale was clustering. GIA argues that more than 95 percent of laboratory grown diamonds entering the market fall into a very narrow range of colour and clarity, a point attributed to Tom Moses, GIA executive vice president and chief laboratory and research officer. GIA's position is that granular natural diamond nomenclature is no longer meaningful for mass produced lab grown.⁴ The institute has also observed that at current lab grown prices, granular certification is harder to justify on cost.²

Stones that do not meet minimum Standard criteria receive no GIA report. The assessment fee is 15 US dollars per carat with a 15 US dollar minimum, the minimum size is 0.15 carats, and the girdle inscription reads "Laboratory grown" plus an assessment number.⁴ The practical buyer impact is that a GIA lab grown report issued after October 1 2025 no longer shows a specific colour or clarity grade, which removes the granularity buyers use to compare stones. To see exact grades on lab grown, buyers now turn to IGI, or to GCAL for cut.⁵

The trade read both ways. Grant Mobley of the Natural Diamond Council called the move "a definitive moment in the ongoing separation of natural diamonds from lab grown diamonds." ALTR chief executive Amish Shah was critical, characterising it as repositioning after failing to dominate lab grown share rather than genuine innovation.² Both readings are in the record; the buyer takeaway is simply that the GIA lab grown report now carries less granularity than it did before.

GCAL competes on rigour rather than volume. It is described as the only gem lab that guarantees its grades in writing and takes financial responsibility if an assessment is found inaccurate. That guarantee, not scale, is the point of the brand.³

Its flagship 8X Ultimate Cut Grade requires an Excellent score across eight separate cut factors, a threshold described as achieved by only about 1 percent of diamonds.³ The result targets the one thing a colour or clarity grade cannot promise, which is light performance. For a buyer who cares most about how a round brilliant returns light, a GCAL 8X report answers a question the other labs do not directly score.

The trade off is coverage. Because GCAL is a boutique, most lab grown diamonds in the market do not carry a GCAL report, and there is no published lab grown market share figure for it. It is a specialist choice layered on top of, not a replacement for, the granular 4Cs grading that IGI provides at scale.

A grading report guarantees less than most buyers assume, and understanding the boundary is the most useful thing on this page. What it does guarantee is an objective, independent assessment of the diamond's characteristics, colour, clarity, cut, carat, polish, symmetry, fluorescence, and proportions, so a seller's description can be checked against the lab's report. It also confirms authenticity and lab grown origin, verified by inscription and screening.⁸

This is why terminology on a listing is not a grade. "Premium" and "near colourless" mean nothing until they are checked against the actual grades on an independent report. The report is the promise; the adjective is not. For a field by field walkthrough of an IGI report, see our guide on how to read an IGI certificate, and for what the grades themselves mean, the 4Cs of colour and clarity.

All three labs are legitimate. They answer different questions, so the right one depends on what you are trying to confirm.

For lab grown at scale with full granular 4Cs grades, IGI is the market standard and the practical default. For a written, money backed grading accuracy guarantee and top tier cut analysis, GCAL 8X. For a Premium or Standard tier from the natural diamond authority, GIA, understanding that after October 2025 you will not see a specific colour or clarity grade on lab grown. The consistent guidance across sources is to compare stones graded by the same lab, and to weigh the actual report rather than the logo.⁷

Every Draco diamond is IGI certified, E to F colour, VS2 and better, and ships with its certificate. The report can be provided on request before purchase, and verified free at IGI.org. Because the grade is fixed to the report, two IGI stones with matching specs are the same diamond, and the only variable left is price. That is also why identical specifications can vary in price between sellers.

The high confidence facts here are drawn from named primary and trade sources with dates. IGI's 65 percent lab grown share and 33 percent overall share come from a direct quote by IGI chief executive Tehmasp Printer, reported by Rapaport on March 11 2025. The GIA October 1 2025 change, its Premium and Standard criteria, the fees, and the effective dates are documented across JCK and Rapaport reporting dated August 27 2025 that quotes the GIA release directly, alongside the GIA press pages. The 95 percent narrow range statistic is attributed to Tom Moses of GIA. GCAL's written guarantee and its eight cut factors come from GCAL's own materials and trade coverage.

The one claim that carries a genuine evidence gap is grading strictness. The direction, GIA more conservative and IGI a step more generous, is consistent across many trade and retailer sources and repeated worked examples. It is not, however, supported by any blind, peer reviewed cross lab study, and none was located for this report. We present it as a directional tendency corroborated by multiple sources, not as a fixed or measured number of grades, and not as Draco's opinion of any lab. The GCAL "about 1 percent achieve 8X" figure rests on a single vendor source and is treated as indicative. Where sources named different GIA leadership titles during a 2025 transition, we have avoided attributing a title we could not confirm. This report will be updated if a controlled study or a corrective primary source appears.