IGI or GIA for a lab-grown diamond? IGI still grades colour and clarity

Is IGI or GIA better for a laboratory-grown diamond?

IGI, if you are comparing one laboratory-grown diamond against another by colour and clarity. Since 1 October 2025, GIA no longer grades a laboratory-grown stone on a letter-by-letter scale. It sorts the stone into one of two bands, Premium or Standard, and stops there. IGI still grades a laboratory-grown stone the way it grades a natural one, on a full colour and clarity scale. That level of detail is what makes its report useful for shopping between stones, beyond simply confirming that one is genuine.

The two labs are no longer doing quite the same job. A GIA Laboratory-Grown Diamond Quality Assessment tells you a stone is well made and puts it in a band. Two different stones, one D colour and VVS clarity with Very Good polish, another J colour and VS clarity, can both land in the same Standard band and read almost the same on paper. An IGI Laboratory Grown Diamond Report keeps the distinction: a letter colour grade on the D-to-Z scale and a clarity grade from Internally Flawless down to Included. If you are trying to work out why one stone costs more than another that looks similar, IGI’s scale gives you the detail to do that. GIA’s Premium or Standard label does not.

One note on wording: the laboratories call this document a report, while most people search for “certificate”. It is the same piece of paper.

Does GIA grade laboratory-grown diamonds?

Yes. GIA has graded laboratory-grown diamonds for years, but the method changed on 1 October 2025. A loose stone of 0.15 carat or larger no longer gets the D-to-Z colour grade or the Flawless-to-I3 clarity grade used for a natural diamond. Instead, GIA sorts it into one of two bands (gia.edu, checked 27 September 2026):

A stone that falls short of Standard gets no GIA assessment at all. Each stone submitted is laser-inscribed on the girdle with “Laboratory-Grown” and its GIA number. GIA gives two reasons for the change: most laboratory-grown stones fall into a very narrow range of colour and clarity, and it no longer wants to describe a manufactured product with a scale created for natural diamonds (gia.edu, checked 27 September 2026).

What does an IGI report say about a laboratory-grown stone?

IGI has graded laboratory-grown diamonds since 2005, and it still assesses one on the full 4Cs: carat weight, colour, clarity and cut. Here is what shows up on the report, and what is worth checking against the actual stone.

For a finished piece of jewellery, IGI’s report also names the precious metal in the mount.

How do you check an IGI report number against the stone?

Start with the number printed on the report. IGI runs its own look-up at igi.org/verify-your-report, where that number calls up a digital copy of the same report you were given. That confirms the paperwork is real and matches IGI’s own record, before you look at the stone at all.

Then check the stone itself. IGI lasers the report number onto the stone’s girdle, the narrow band around its widest point, so a jeweller can match a loose stone to its report. That inscription is cut at a scale you cannot read with the naked eye. You need a jeweller’s loupe, or the microscope a workshop already uses to set the stone. Line the stone up under magnification, and the number should read exactly like the one on the page.

A full step-by-step checklist is in how to check an IGI report.

What a laboratory report does not tell you

An IGI report is not a valuation. Asked directly whether a certified stone can be appraised, IGI’s own answer is that a report “provides objective information about the diamond’s characteristics but is not itself an appraisal.” Appraising a stone, working out what it is worth, is a separate step done afterwards by a valuer, not by IGI or GIA.

A report also does not cover a whole ring: it is written for the stone submitted for grading. ENBOM DIAMONDS works the same way: a centre stone of 0.30 carat or larger comes with its own independent laboratory report, and smaller, side and pavé stones do not (more on that below).

A seller’s certificate is not an independent report

A certificate written by the seller is not the same thing as an independent laboratory report. One is the shop grading its own stock. The other is IGI or GIA, with no stake in whether you buy.

Before you pay for a ring, I would ask three things: does the stone have an independent laboratory report; what exactly is the cut; and what exactly am I paying extra for. Under bright shop lights, every stone can look perfect. For a simple band, a classic stud or a traditional tennis bracelet, I also would not pay extra for a big brand name. You are getting the same gold and the same stone either way, and the report is what actually tells you what you bought.

What is worth paying extra for in a report

Colour and clarity move the price more than they move what you can see. If a VS1 or VS2 stone costs noticeably less than a VVS1 or VVS2 next to it, I would choose the VS: in most cases you will not see the difference with the naked eye. Most of the lab-grown stones I set are VVS1 or VVS2; when a VS costs noticeably less for a stone that looks the same, I take the VS. Colour works the same way. D costs noticeably more than E, and the difference between them is very hard to see once the stone is set. GIA’s own explanation for dropping the letter grades, mentioned above, is that most laboratory-grown stones already sit in a narrow band of colour and clarity to begin with, which is exactly why I would not pay a premium for the very top of that band.

Cut is where I would spend the money instead. Two stones of identical carat weight can look different in size from above, because a deep cut hides weight underneath, where you cannot see it. A report states the cut and the measurements together, so you can check whether you are looking at a stone cut for its face-up size or one cut to protect its carat weight. That is the figure worth reading closely, more than the band at the top of the page.

How ENBOM DIAMONDS handles laboratory reports

At ENBOM DIAMONDS, lab-grown stones come with an IGI report and natural stones with a GIA report; most of the stones I use are lab-grown and graded by IGI. For a centre stone of 0.30 carat or larger, the report is included in the price. Smaller, side and pavé stones are not individually reported.

If you are working out how a report fits into the rest of a custom order, the timeline is laid out in how long a custom engagement ring takes. Tell me the size and shape of the centre stone you are considering, and I’ll quote it, with the report included if the stone is 0.30 carat or more.

A natural diamond is a different question

Everything above is about a laboratory-grown stone. For a natural diamond, GIA’s 2025 change does not apply: it concerned laboratory-grown stones only, and the colour and clarity scale it stopped using for them was created for natural diamonds in the first place (gia.edu, checked 27 September 2026). Which laboratory to choose for a natural stone is a separate question from the one this article answers.

ENBOM DIAMONDS sources natural stones by request, alongside laboratory-grown ones, subject to availability for the specific piece. Whether the stone is laboratory-grown or natural, ask which laboratory’s report comes with it before you pay.