IGI Report Check, Verifying a Lab-Grown Diamond Certificate

More than nine in ten certified lab-grown diamonds in our index carry an IGI report. So if you're buying lab-grown, the most useful thing you can learn is how to check one properly. Glancing at a PDF the retailer emailed you doesn't count.

This post sits under our broader guide to finding a diamond certificate number when the retailer hides it, which covers every lab and every trick retailers use to keep you from comparing. Here we stick to IGI: what an IGI report check actually proves, how to run one in a few minutes, and the ways listings get the report wrong.

What a check proves, and what it doesn't

An IGI certificate check confirms that a report with that number exists in IGI's database, and shows you the stone it describes. Carat weight to two decimal places. Colour and clarity. A cut grade if it's a round. Measurements to the hundredth of a millimetre, plus table and depth percentages. The growth method (CVD or HPHT) and IGI's comment on whether there's any sign of post growth treatment.

What it can't prove is that the stone in your box is the stone on the report.

That link comes from the laser inscription on the girdle. On IGI lab-grown stones the inscription carries the report number, normally with an "LG" prefix. Most good online retailers publish an inscription photo or a magnified video; if yours doesn't, any jeweller with a loupe can read it in under a minute. Without that match, a verified report is just a verified piece of paper.

We see buyers do the first half all the time. The second half gets skipped far more often than it should.

Running an IGI report check, step by step

The whole process takes about five minutes once you have the number. Four steps, in this order.

1. Get the report number. It should be on the listing, on the report PDF, and inscribed on the girdle. All three should match. If the retailer won't show it, skip ahead to the last section before going further.

2. Verify the IGI certificate on IGI's own site. Go to igi.org, find the report verification page, and enter the number exactly as printed. Don't trust a PDF link the retailer sends you; type the number in yourself. Then compare every field against the listing, not just the four Cs. Measurements matter here because they're the hardest thing to fudge. Two stones can share a carat weight, colour and clarity, but they won't share measurements to the hundredth of a millimetre.

3. Run it through our IGI report check. IGI's page tells you what the stone is. Our decoder tells you what those fields mean for the price: which grades are sitting at a value sweet spot, which ones you're paying a premium for, and which proportions are worth a second look.

4. Do an IGI report number lookup across retailers. Our cross-lab lookup searches the report number against every listing in the index, across more than 110 retailers. Lab-grown inventory gets shared widely, so the same physical stone can appear on several sites at once. When it does, you'll see every asking price side by side. Same stone, same report, different number on the price tag.

That fourth step is where the money is. A report check tells you the stone is real. A cross-retailer lookup tells you whether you're about to overpay for it.

And if the lookup shows the same report number listed with different specs on different sites? Stop. One of those listings is wrong, and you need to know which before you pay anyone.

What the report fields mean for price

IGI lab-grown stones have a median of $346 per carat across our index. That's the cheapest certified segment of any real size we track. (GSI lab-grown sits at $341, but on only 1,018 stones it's a rounding error next to IGI's 5,143,529.)

At that price level, the fields on the report don't move price the way they do with natural diamonds. High colour and clarity grades are abundant in lab-grown, because growers can produce them reliably. An E VVS2 isn't a rare find; it's a normal Tuesday. So the premium for climbing from G to E, or from VS1 to VVS2, is compressed compared with natural stones, and paying a big jump for top grades is usually money poorly spent.

What does matter more:

• Carat weight, and specifically where it falls. A report reading 0.98 tells a very different price story to one reading 1.01, even though nobody could see the difference across a dinner table.
• Cut grade and proportions. On rounds, IGI issues an overall cut grade. On fancy shapes it doesn't, so the measurements, depth and table do the talking. A well-cut oval with a sensible length to width ratio is worth more to your eye than a higher clarity grade.
• Growth method and treatment comment. IGI notes whether the stone shows signs of post growth treatment. Many CVD stones are treated after growth to improve colour. That's standard practice and not a defect, but it belongs on the listing, and a stone noted as showing no indication of treatment is something some buyers will reasonably prefer.
• Fluorescence, which is far less of a price lever in lab-grown than in natural, but should still match between listing and report.

Our guide to decoding an IGI certificate for lab-grown diamonds goes field by field through the report layout if you want the full walkthrough.

Where IGI sits against GIA and GCAL

IGI dominates lab-grown grading in our index by a distance. Here's how the labs compare on volume and median price per carat.

IGI's lab-grown book is roughly twenty times the size of GIA's lab-grown book. That's the whole story of lab-grown certification right now. GCAL is a distant third.

The medians need careful reading, though. GIA lab-grown stones sit at $971 per carat, nearly three times IGI's $346. That doesn't mean a GIA report adds that much value to an identical stone. A median reflects the mix of stones each lab grades, not a like for like price on matching specs. If you want the head to head on matching stones, our GIA vs IGI lab-grown comparison does exactly that. Our view: never pay a lab premium until you've compared stones with the same specs from both labs.

Now look at the uncertified lab-grown row. A median of $950 per carat. That's well above IGI's median, for stones with no independent report at all. Uncertified doesn't mean cheaper, and with no report you can't check anything we've described above. We'd walk past those.

IGI isn't only a lab-grown lab, either. It grades 365,002 natural stones in our index at a median of $1,448 per carat, against GIA's $1,988 on natural. Same caution about mix applies. But it's a reminder that an IGI report on its own doesn't tell you the stone is lab-grown; the report itself does, and you should read that line first.

Six ways listings misquote an IGI report

These are the mismatches we see between listings and the reports they claim to describe. None of them are exotic.

Carat rounding. The report says 1.47, the listing headline says 1.5. That's not a small thing. Carat weight is a primary price driver, and a stone just under a round number should be priced like one.

A cut grade the report never gave. IGI's overall cut grade applies to rounds. If a pear or cushion listing says "Ideal cut", that word came from the retailer's marketing team, not from IGI. Check the report for polish and symmetry instead.

"IGI certified" with no number. A lab name in a listing title is a claim, not a certificate. If there's no report number you can type into IGI's site, treat the listing as uncertified.

Transcription errors in colour or clarity. Usually innocent: a G typed as an F, a VS2 typed as a VS1. Usually in the retailer's favour, too, which is less charming. Read the grade off IGI's site, not the listing.

Treatment left off. The report notes post growth treatment, the listing doesn't mention it. Not a dealbreaker on its own, but it's information you were entitled to see before choosing.

Measurements that don't match. This is the serious one. If the listing's measurements differ from the report's, the listing may be pointing to a different stone's report entirely. Ask for the inscription photo before going any further.

When the retailer hides the report number

Some retailers hide report numbers on purpose. The reason is simple: a number lets you run an IGI cert lookup, find the same stone elsewhere, and compare prices. Hiding it protects their margin, not your interests.

Ask for the number in writing before paying a deposit. A reputable retailer will send it within the hour. If they say it's only available after purchase, that tells you everything about how confident they are in their price. You can also ask for a photo of the girdle inscription, which shows the number whether they like it or not.

If they still won't share it, the parent guide linked at the top of this post covers every other route we know for tracking it down. And if none of those work, buy the stone from someone who isn't hiding anything. With more than five million IGI graded lab-grown stones in our index, there's always another one.

What we're watching

Two numbers. First, GIA's 2.4% share of the index in lab-grown. If that climbs meaningfully, the lab-grown market will start pricing a real difference between the two labs, and the IGI vs GIA question gets more interesting for buyers. Second, the $346 IGI median itself, which sets the baseline for what a fair lab-grown price looks like across the whole market.

Until then, the playbook doesn't change. Get the number. Check it on IGI's site. Run it through our lookup. Five minutes of checking against more than five million stones is the best price protection a lab-grown buyer has.