IGI or SGL, settled
IGI, and it is not close. Both are real laboratories with real gemmologists, but a grading report is a claim that other people have to accept, and the trade accepts IGI everywhere. SGL is an Indian lab with almost no standing outside its home market, which means nobody you later deal with, an insurer, a valuer, a buyer, has a reference point for what its grades mean.That is the whole test for a lab. Not the paper stock or the hologram. Can a stranger read this report and know what they are looking at? If a stone is only available with an SGL report, treat the grades as the seller's opinion and price it accordingly.
The labs worth knowing
There are hundreds of gemmological laboratories. Five or six matter to someone buying an engagement ring in Australia, and they sort into a clear order.One name you will still see quoted is AGS, which ran the best cut research in the industry for decades. Its laboratory closed in 2022 and GIA took on its work, so an AGS report means an older stone, not a current lab.
GIAThe benchmark
The Gemological Institute of America, a non-profit that wrote the colour and clarity scales everyone else uses. Strictest and most consistent on natural stones. Every other lab is measured against it.IGIWidely accepted
Antwerp, 1975. Grades most of the lab-grown diamonds sold in the world, including ours. Consistent enough to buy from, generally a touch softer than GIA on colour and clarity.GCALWidely accepted
A smaller New York lab that publishes light-performance testing alongside the grades and guarantees them. Uncommon in Australia, credible when you see it.HRD AntwerpWidely accepted
The European counterpart to GIA, run out of the Antwerp diamond district. Solid work, rarely crossing paths with an Australian buyer.SGLThin outside its market
Solitaire Gemmological Laboratories, an Indian lab with real equipment and gemmologists but little standing in the wider trade. A report nobody outside its home market benchmarks against tells you very little.EGLWe would not rely on it
Long history of grades two or three steps softer than GIA on the same stone. One of the big trading networks banned its reports in 2014 and the reputation has not recovered.The honest short answerMost reputable, most trusted, best: all three questions have the same answer, which is GIA. For a lab-grown diamond, IGI is the practical answer, because that is what the stones come with and the grading is consistent.
Is GIA actually stricter than IGI?
Yes, and the gap is smaller than the internet suggests. They are separate organisations with separate graders. GIA is an American non-profit founded in 1931 that invented the D-to-Z colour scale and the clarity grades; IGI is a commercial lab founded in Antwerp in 1975. Same vocabulary, different hands applying it.Send the same stone to both and the IGI report will often come back one step brighter on colour or one step cleaner on clarity. Occasionally two. Colour is judged by eye against master stones, so a small, consistent difference in house standard shows up as a whole grade on paper. That is why a G VS1 from IGI and a G VS1 from GIA are not quite the same stone, and why GIA-graded natural diamonds sell for more than the grades alone would explain.What this means in practice: compare IGI stones against IGI stones. Do not put an IGI report next to a GIA report, notice the GIA stone costs more for the same letters, and conclude you found a bargain. And if you are buying a natural diamond of real size, a GIA report is worth the premium, because that is the document the resale market wants.Grades are also not the whole stone. Cut is what you actually see, and cut grade is measured from proportions rather than judged by eye, which makes it the most comparable number on either report.
Who grades lab-grown diamonds
Almost every lab-grown diamond you will be shown carries an IGI report. IGI committed to grading lab-grown stones years before its competitors took the category seriously, and it now grades the large majority of them worldwide, including ours.GIA does still examine lab-grown diamonds, but it has moved that work away from letter-and-number grading toward broad descriptive categories rather than the D-to-Z and VVS-to-I scales it uses for mined stones. Its stated reasoning is that lab-grown production clusters so tightly at the top of both scales that the fine distinctions stop carrying information. Whether you find that persuasive or protective of the mined market probably depends on what you already thought of GIA.Either way, it is not a reason to worry about an IGI-graded lab-grown stone. It is the reason IGI became the standard for the category.
What a report costs, and who pays
Grading a one-carat stone at GIA runs to roughly a hundred US dollars, scaling up with weight and the level of detail. Send a stone yourself from Australia and the fee is the small part: insured freight both ways and several weeks without the stone cost more than the grading.IGI charges less, works faster, and grades at volume for the growers themselves, which is where the price difference comes from. Not looser standards, or not only that: a lab embedded in the production chain handles thousands of stones a week without freight, insurance or retrieval, and it prices accordingly.You never pay a grading fee as a line item. It is inside the stone price, and it is a rounding error next to the price gap between a GIA-graded and an IGI-graded natural diamond. That gap is market confidence, not laboratory overhead.
Fake reports, and checking a real one
Forged IGI and GIA reports exist. So do genuine reports photocopied and attached to a different, lesser stone, which is the more common trick and the harder one to spot. Neither is a reason to distrust the labs. Both are a reason to verify rather than admire the document.Do this in the shop, not at home. Any jeweller who is unhappy about you pulling up the lab's lookup page on your phone has told you something more useful than the report would have.The same check is what makes buying online safe. A report you can verify on the laboratory's own website, from a seller with a returns policy you have read, is more reliable than a handshake and a certificate in a drawer. Verify the paper, then judge the seller on their returns terms and what they will put in writing.Not every diamond comes with a report, and small stones usually do not. Melee under about 0.20ct is sold in parcels by quality range because individual grading would cost more than the stones. Any centre stone worth grading should arrive graded; if a jeweller cannot produce a report for one, ask why, and expect a straight answer rather than an in-house appraisal on their own letterhead.
1Find the report numberPrinted on the report, usually top right. Seven to ten digits, no spaces.
2Look it up on the lab's own siteGIA and IGI both publish a free report lookup. The stone's shape, weight, colour, clarity and cut must match the paper in front of you, digit for digit.
3Read the girdle inscriptionMost graded stones carry the report number laser-etched on the girdle. Ask the jeweller to show it to you at 10x. It should be the same number.
4Check the measurements against the stoneMillimetre dimensions and weight are the hardest things to fake, because they have to match the physical stone. A swapped stone fails here.
The four types of diamond
This question gets asked in two different senses, and the answers are unrelated.Gemmologists sort diamonds into types Ia, Ib, IIa and IIb by what trace elements sit in the carbon lattice. Type I contains nitrogen, which is most natural diamonds and is what makes them faintly yellow. Type IIa is nearly pure carbon, which is rare in nature, common in lab-grown stones, and the reason lab-grown diamonds are so often colourless. Type IIb contains boron, conducts electricity, and reads blue. A screening device is largely sorting Type I from Type II, which is why a colourless natural diamond sometimes gets flagged for further testing.The other sense is the four things sold as diamonds: natural, lab-grown, treated (a real diamond whose colour or clarity has been altered), and simulant (moissanite or cubic zirconia, which are not diamond at all). A report names which of these you have, and that single line is the most important sentence on it. See how a laboratory proves origin for how they can be so certain.
What we put in front of you
Our lab-grown centre stones usually come with an IGI report, and our natural ones with a GIA report. Either way, we give you the report number before you buy so you can check it against the laboratory's own database yourself. The inscription is on the girdle of the stone that arrives.If you are weighing up a stone from somewhere else and the report is from a lab you have not heard of, send us the number and the grades. We will tell you what we think the stone is, including when the answer is that it looks like a good buy.
Not sure about a certificate?Send us a photo of the report. We will tell you whether the lab is one to rely on, what the grades mean for how the stone will look, and whether the price makes sense.
Online consult
