IGI vs GIA: Which Diamond Grading Report Should You Trust?
For natural diamonds, a GIA report is the most widely recognised benchmark, and IGI is a well-known alternative. For lab-grown diamonds the picture changed in October 2025: GIA now labels lab-grown stones only "Premium" or "Standard" instead of giving colour and clarity grades, while IGI still grades them on the full 4Cs scale and states the growth method.
That difference matters when you are comparing stones online. Two lab-grown diamonds can look identical on a product page while one comes with a detailed IGI report and the other with a two-word GIA assessment. This guide explains what each lab does, how to read the lines that actually affect price and appearance, and how to check that the report in front of you belongs to the stone you are buying.
What is a diamond grading report?
A grading report (often called a "certificate" or "cert") is an independent lab's description of one specific stone: its shape, measurements, carat weight, colour, clarity and, for round brilliants, cut. It is not an appraisal and it does not state a dollar value. For insurance you still need a separate appraisal; our guide to jewellery insurance in Canada covers that side.
The value of a report comes from independence. The seller's own description can be optimistic. A lab that has never met the buyer or the seller has no reason to be.
Who are GIA and IGI?
GIA (Gemological Institute of America) is a non-profit founded in 1931. It created the 4Cs and the D-to-Z colour scale that the rest of the industry now uses, which is why its natural diamond reports are treated as the reference point.
IGI (International Gemological Institute) was founded in Antwerp in 1975 and grades both natural and lab-grown diamonds. It is one of the labs you will see most often on lab-grown stones.
Both are legitimate, independent labs. The real differences are in how they treat lab-grown stones and in how buyers and resellers perceive their grading on natural ones.
IGI vs GIA for natural diamonds
For a natural (mined) diamond, both labs use the same 4Cs framework. GIA is generally regarded in the trade as the stricter and more consistent grader, and GIA-graded natural diamonds usually carry a price premium as a result. A natural diamond graded G colour by IGI is not guaranteed to receive the same grade from GIA; buyers comparing natural stones across labs often treat an IGI grade with a little caution, or compare against GIA-graded stones of the same listed grades.
If you are buying a natural diamond above roughly a carat and resale or insurance replacement matters to you, a GIA report is the safer default. For a smaller natural stone, an IGI report is perfectly usable as long as you judge the stone with your own eyes and a good video.
IGI vs GIA for lab-grown diamonds: what changed in 2025
In June 2025, GIA announced that it would stop using natural-diamond colour and clarity grades for lab-grown stones, explaining that more than 95% of lab-grown diamonds fall into a very narrow range of colour and clarity. Since October 1, 2025, GIA issues a Laboratory-Grown Diamond Quality Assessment with one of two descriptions:
| GIA category | Colour | Clarity | Polish | Symmetry | Cut (round brilliant only) |
|---|---|---|---|---|---|
| Premium (must meet all) | D | VVS or higher | Excellent | Excellent | Excellent |
| Standard (minimums) | E to J | VS | Very Good | Very Good (Good for fancy shapes) | Very Good |
A lab-grown stone that misses any Standard minimum gets no GIA assessment at all. Assessed stones (0.15 carat and up) are laser-inscribed on the girdle with "Laboratory-Grown" and the GIA number. Lab-grown reports GIA issued before the change remain valid.
IGI took the opposite route. An IGI Laboratory Grown Diamond Report still gives a specific colour grade (D, E, F and so on), clarity grade (VVS1, VS2 and so on), cut grade for rounds, polish, symmetry and fluorescence. It also states the growth method (CVD or HPHT) and, since 2021, whether the stone is "As Grown" with no indication of post-growth treatment, or shows indications of post-growth treatment. The girdle is typically laser-inscribed with "LABGROWN IGI" and the report number.
Side by side: IGI vs GIA on a lab-grown diamond
| What you want to know | IGI lab-grown report | GIA lab-grown assessment (since Oct 2025) |
|---|---|---|
| Exact colour grade (D, E, F...) | Yes | No: D or E-to-J range only |
| Exact clarity grade | Yes | No: VVS+ or VS range only |
| Cut, polish, symmetry | Yes | Used to set the category |
| Growth method (CVD/HPHT) | Yes | Not part of the published criteria |
| Post-growth treatment noted | Yes ("As Grown" or not) | Not part of the published criteria |
| Girdle inscription | "LABGROWN IGI" + report number | "Laboratory-Grown" + assessment number |
| Stones below VS or J | Graded normally | Not assessed |
Which is better for a lab-grown diamond, IGI or GIA?
For most lab-grown engagement ring buyers, an IGI report gives you more usable information. When you are choosing between an E VVS2 and a G VS1 at different prices, you need the actual grades, and the new GIA document will call both of them "Standard". A GIA assessment does tell you the stone cleared a published quality floor, which some buyers like, and a "Premium" designation is a simple way to know you have a top-colour, top-clarity, well-cut stone.
What we would not do is pay extra for a lab-grown diamond just because of the lab name on the paper. With lab-grown prices where they are, and lab-grown resale value very limited (we covered this in our lab-grown engagement rings guide), the stone in front of you matters more than the logo.
How do you read a diamond grading report?
These are the lines worth slowing down for, in roughly the order they appear:
- Report number. Use it to verify the report online (see below) and to match the girdle inscription.
- Shape and cutting style. "Round brilliant", "oval brilliant", "emerald cut" and so on.
- Measurements. Length, width and depth in millimetres. For elongated shapes, divide length by width to get the ratio, which shapes the look far more than carat weight does.
- Carat weight. Weight, not size. Two 1-carat stones can face up at noticeably different diameters depending on depth.
- Colour and clarity. On an IGI lab-grown report these are the familiar D-to-Z and FL-to-I scales. On a new GIA lab-grown assessment you will see Premium or Standard instead.
- Cut, polish and symmetry. IGI uses "Ideal" as its top cut grade for rounds; GIA uses "Excellent". For fancy shapes, neither lab issues an overall cut grade, so polish and symmetry carry more weight.
- Fluorescence. "None" or "Faint" is the safe choice; strong blue fluorescence can make a few stones look slightly hazy.
- Comments. On lab-grown stones this is where you will find the growth method and whether the stone is as grown or treated.
- Inscription. What is laser-written on the girdle. It should match the report number.
How do you verify a GIA or IGI report?
Both labs have free online lookups. GIA's Report Check lets you enter the report number and compare the result with the seller's listing; GIA's own advice is to make sure the online description matches the grading results. IGI has a similar "verify your report" lookup on igi.org. Then confirm that the girdle inscription matches the number. It is visible under 10x magnification, and any jeweller can show it to you with a loupe or microscope in a minute.
If a seller can't give you a report number, or the number doesn't match the stone, walk away.
What Canadian buyers should watch for in listings
The Canadian Jewellers Association's advertising guidelines for lab-grown diamonds, written with the Competition Act in mind, say a lab-grown stone must be described with "laboratory-grown", "lab-created" or "synthetic" placed immediately before the word "diamond", and that "diamond" used on its own means a natural diamond. If a listing just says "diamond" and the price looks like a lab-grown price, ask the seller to confirm the origin in writing and check the report: both labs state clearly when a stone is lab-grown.
Moissanite is a separate gemstone, not a diamond, so neither of these diamond reports applies to it. If you are weighing the two, start with our moissanite vs lab diamond comparison.
Choosing a certified stone with Toronto Fine Jewelry
Every listing in our loose diamond collection shows the carat, colour and clarity and links to the stone's independent GIA or IGI report, so you can check the paperwork yourself before anything is set. If you would like help reading a report or comparing two stones, bring the report numbers to a consultation at our Mississauga studio near Square One or book a video call, and we can go through them with you. Once you have chosen, we set the stone in one of our designs or a custom setting, with casting, setting and polishing taking 4 to 6 weeks from design approval. Book a consultation to get started.
Shopping for an engagement ring this season? Sign up on this page for $100 off an engagement ring of $1,000 or more, valid for 30 days.
Frequently asked questions
Is IGI as good as GIA?
Both are independent, respected labs. For natural diamonds, GIA is widely seen as the stricter benchmark. For lab-grown diamonds, IGI reports currently give more detail, because GIA now only labels lab-grown stones Premium or Standard.
Does GIA still grade lab-grown diamonds?
Yes, but differently. Since October 1, 2025, GIA issues a Laboratory-Grown Diamond Quality Assessment that classifies stones as Premium or Standard instead of giving specific colour and clarity grades. Stones below the Standard minimums are not assessed.
What does "As Grown" mean on an IGI report?
It means IGI found no indication of post-growth treatment, such as the heat treatment sometimes used to improve the colour of lab-grown diamonds. IGI reports also state whether the stone was grown by CVD or HPHT.
Is a diamond certificate the same as an appraisal?
No. A grading report describes the stone's characteristics; it does not give a value. Insurers usually ask for a separate appraisal that states a replacement value.
How can I tell if a diamond matches its report?
Look up the report number on the lab's website, check that the measurements and grades match the listing, and confirm the laser inscription on the girdle matches the report number under magnification.
Are GIA-graded lab-grown diamonds worth paying more for?
Usually not on their own. Judge the actual stone, its measurements and its grades. A Premium designation is a reassurance of top colour and clarity, but an IGI report with the same grades tells you as much or more.