IGI or GIA for Lab-Grown Diamonds From Surat?

An IGI report is usually enough for a Surat lab-grown stone. It's the report most Indian growers ship with, and the trade accepts it. What makes it enough is two lines that IGI adds only when asked, the growth method and any post-growth treatment, so the real question isn't which lab but what you asked the lab to say.

The comparison buyers usually want has also changed under them. For years the trade line was that IGI grades about a step more generously than GIA. A US retailer put it this way in 2024: "You can get a D color from IGI and maybe GIA will grade it E color but it's still colorless" (r/LabDiamonds, March 2024 (opens in a new tab), from our forum signal log). Since October 2025, GIA no longer gives lab-grown stones a D-to-Z colour grade at all. Our lab-grown diamonds from India page covers supply, disclosure law and duty, and our diamond certificates guide covers which paper proves what. This article is only about the two reports. The caveat - we read both labs' own published descriptions, not a sample of reports, and lab formats change.

1. What Did GIA Change in 2025?

Its whole approach to colourless lab-grown stones. GIA's argument is that most grown stones "fall into a very narrow range of color and clarity", so it now gives an overall assessment instead of a grade (GIA, August 2025 (opens in a new tab)). The criteria in its October 2025 chart are short (GIA assessment criteria (opens in a new tab)) -

A stone has to meet Premium on all five to be Premium. A mix of Premium and Standard makes it Standard. Fall outside on any one, and there's no GIA assessment at all. The service covers loose, colourless to near-colourless stones of 0.15 carats and up, and each stone is laser-inscribed with "Laboratory-Grown" and the assessment number.

So what does this mean for a Surat parcel? An F, VS1 stone with an IGI report would, if it met the cut and polish minimums, come back from GIA as "Standard". So would a J, VS2. The GIA document simply doesn't distinguish them. If your customers shop by colour letter, a GIA assessment gives them less to compare, not more.

One warning. GIA's site still carries older pages describing its earlier lab-grown reports with 4Cs grades. When a supplier offers "a GIA report", ask which document and what date, because a pre-October 2025 report and a 2026 assessment are different things.

2. What Does an IGI Lab-Grown Report Tell You?

A full grade on the scales the trade already uses. IGI's lab-grown report sets colour on the D-to-Z scale, from D to F colourless through G to J near colourless and on down, with clarity and cut grades alongside (IGI (opens in a new tab)). IGI says it screens every stone to decide whether it's mined, lab-grown or a simulant before grading.

The part that matters for your order is the comments section. IGI notes the growth process and the presence of treatments there "upon request". So an IGI report without a CVD or HPHT line isn't necessarily the lab hiding anything. It may simply be what the grower ordered. That's why the buyer quoted above never got an answer. The fix is cheap. Write it into the purchase order that every report must state the growth method and whether post-growth treatment was detected, and reject reports that don't.

3. Is IGI Really More Lenient?

Some traders think so, others say it's a myth, and our forum log has both. One 2025 voice said to "stay away from IGI at all costs" (our forum log, May 2025), while a US buyer said the best supplier they'd found for lab-grown stones "is Indian and uses IGI certs" (r/labdiamond, May 2024 (opens in a new tab)). We haven't measured it, and nobody we read has published a controlled comparison.

Two things are certain, though. The old "one colour grade softer" test can't be run against current GIA output, because GIA no longer issues a colour grade for these stones. And the only way to know how your own parcels grade is to send a few to a second lab before you place a large order. Pick five stones across your colour and clarity range, get them graded twice, and you'll know more than any forum thread can tell you.

4. Why Does the Growth Method Line Matter So Much?

Because CVD and HPHT stones fail differently, and your incoming checks follow the method. Buyers in our log say the cheapest stones are "usually CVD with post growth treatment", that CVD can look brown or hazy, and that HPHT stones can carry a blue tint and "sometimes test as moissanite on most diamond testers" (r/LabDiamonds, March 2023). That last point bites at a retail counter. A customer's handheld tester reading "moissanite" on a stone you sold as a diamond is a bad afternoon, and the report line saying HPHT is your explanation.

Treatment is the other half. Post-growth treatment to improve colour is legal and common. It just has to be known, because it bears on price and on what you tell the customer. A report that states "as grown" or names the treatment gives you that answer in writing, per stone. Our lab-grown page explains the two methods in more depth.

5. How Do You Know the Report Belongs to Your Stone?

Check three things, not one. Both labs let you look up a report by number. GIA's own page says its Report Check confirms "that the information on your report matches what is archived in the GIA report database" (GIA (opens in a new tab)), and IGI runs its own verification. That proves the report is real. It doesn't prove the stone in the parcel is the stone on the report.

So match the girdle inscription under a loupe, the carat weight to two decimals, and the measurements, against the report. If any of them disagree, the report describes some other stone. The same discipline applies to coloured gems and their labs, which our article on checking material claims from India covers.

6. So Which Should You Ask For?

Start from who buys from you, not from the lab's reputation.

• Selling to jewellers or consumers who shop by colour and clarity letters? IGI gives them the letters. Require the growth method and treatment lines.
• Selling a premium brand whose customers ask for GIA by name? A GIA assessment works for D-colour, VVS stones that come back Premium. For E to J, your customers get "Standard" and no letter, so make sure your listings explain that.
• Buying many small stones? Ask your supplier how reports are issued below 0.15 ct, because GIA's assessment doesn't go below that weight. Agree in writing whether you get a report per stone or per parcel.

Whichever you choose, name the lab in the order before you see stones, so a supplier can't pick the lab after grading. If you'd like someone in Surat to sit in on the parcel check, confirm inscriptions and match reports before the stones leave, SourcingSync (opens in a new tab) does that. The fair where most foreign buyers meet Surat firms, and how the town's trade works, are on the Surat diamond cluster page.

Questions Buyers Ask