IGI Certificates for Lab Grown Diamonds, and How to Read One

An IGI certificate is a grading report from the International Gemological Institute: an independent laboratory assessment of one specific stone, describing its measurements, weight, colour, clarity, cut quality and identifying features. It is not a valuation, not a guarantee of value, and not an opinion about whether the ring is good. It is a description, produced by people who have no stake in the sale.

Every lab grown diamond we set is IGI certified, and every one is laser inscribed on the girdle with its report number, so the paper and the stone can be matched by anyone with a loupe. Below is how to read the document, how to check it yourself, and what it will not tell you.

IGI and GIA both grade lab grown diamonds

They do. This is worth stating plainly because a lot of what is written online implies otherwise.

The reason IGI dominates lab grown grading is partly historical and partly practical. IGI began issuing full grading reports for lab grown diamonds early, at a point when GIA was more cautious about the category and used a more limited style of report, describing lab grown stones in broader ranges rather than the exact grade by grade format used for mined diamonds. Growers and retailers wanted the familiar 4Cs presentation buyers already recognised, so the supply chain built itself around IGI. IGI also had a large presence in the cutting centres where these stones were being finished, which mattered for turnaround.

GIA has since moved to full grading for lab grown diamonds. So the modern situation is simple: both laboratories grade lab grown diamonds, both issue detailed reports, and IGI got there first and kept the volume.

What that means for you as a buyer:

• A lab grown diamond with an IGI report is not a lesser stone than one with a GIA report. It is the industry norm.
• The answer to "are lab grown diamonds GIA certified" is yes, they can be. Many are not, because the trade standardised on IGI.
• Grading is human judgement applied to a scale, and laboratories differ slightly in how strictly they apply it. Across any two labs, colour and clarity grades sit within a grade of each other more often than exactly on top of each other. That is normal, and it is why you should compare stones graded by the same laboratory when you are comparing closely.
• Neither report tells you what the stone looks like.

I would not choose a ring based on which of the two graded it. I would choose based on the stone in front of me, and use the report to confirm what I am being told about it.

Reading the report, field by field

Pull up the report for the stone you are considering and go through it in this order.

Report number. A unique identifier for this document and this stone. On a lab grown diamond it is also laser inscribed on the girdle. Write it down, because it is what you use to verify the report independently.

Date. When the stone was graded. Old is not a problem. The stone has not changed.

Description or growth method. The report will state that the stone is laboratory grown, and typically whether it was grown by CVD or HPHT. Both produce real diamond. If you want the detail on how they differ, CVD versus HPHT covers it, and how lab grown diamonds are made covers the process end to end. It does not change how the stone looks on a hand.

Shape and cutting style. For example "Round Brilliant", "Oval Brilliant", "Emerald Cut, step cut". The cutting style matters: brilliant cuts are faceted to scatter light, step cuts are faceted in long parallel planes that behave like windows. Step cuts hide far less, which changes which grades you should protect.

Measurements. Length by width by depth, in millimetres, to two decimal places. People skip this field and it is one of the most useful on the page. Carat is weight, not size. Measurements tell you how big the stone will look. Two stones of identical carat weight can differ noticeably across the top, because one carries more of its weight in depth.

Carat weight. To two decimal places. Weight sits on price thresholds: a 0.98ct and a 1.01ct look identical and are not priced identically.

Colour grade. D through Z, with D the most colourless. Grading is done face down against masterstones under controlled lighting, which is not how anyone looks at a ring. Face up, in a setting, in ordinary light, the differences compress dramatically.

Clarity grade. FL, IF, then VVS1 and VVS2, VS1 and VS2, SI1 and SI2, then the I grades, describing inclusions under 10x magnification. "Eye clean" is not a grading term, it is a judgement about what you can see without a loupe, and plenty of VS2 and SI1 stones are eye clean.

Cut grade. Excellent, Very Good, Good and downward. On round brilliants this is a full assessment of proportions and light performance, and it is the most important grade on the report, because it is the one visible from across a room. Many fancy shapes receive no overall cut grade at all, which is why polish and symmetry matter more in oval, pear and marquise.

Polish. The quality of the surface finish on the facets. Look for Excellent or Very Good.

Symmetry. How precisely the facets align and how even the outline is. On pointed shapes this is what determines whether the point looks straight or slightly off. Do not accept Good symmetry on a pear or a marquise.

Fluorescence. How the stone reacts under ultraviolet light. Usually None or Faint on lab grown diamonds. In most cases it is a non issue at these levels.

The plot. A diagram of the stone from above and below with the inclusions marked, colour coded by type: crystals, feathers, clouds, pinpoints. Read the plot, not just the grade. An SI1 with its inclusion sitting under a claw is a better buy than a VS2 with a feather in the middle of the table. The plot tells you where, and where is what matters.

Comments. Easy to ignore, occasionally the most important line on the page. This is where the laboratory records things that do not fit elsewhere, including notes about clouds or graining that affect transparency, and confirmation of the laser inscription.

Girdle inscription. The report will state the inscription. On our stones this is the IGI report number, engraved into the girdle at a scale that needs magnification to read. It is how you confirm the stone in your ring is the stone on your paperwork.

How to verify a report yourself

Do this. It takes a minute and it is the single most useful thing in this article.

1. Get the report number, from the certificate or from the product page. Any retailer should give it to you before you buy.
2. Go to igi.org and find their report check or verify tool.
3. Enter the report number.
4. Compare what comes back on screen against the document you were given. Shape, carat, colour, clarity, cut, measurements. All of it should match exactly.

You are checking two things: that the report exists, and that the document you were handed has not been altered. Both are worth confirming, and neither requires you to trust the seller.

Then, when you have the ring, ask to see the girdle inscription under magnification and check the number matches. Any competent jeweller can show you this in thirty seconds. We do it as a matter of course.

If the number does not come up

Do not panic and do not accept a vague explanation. Work through it in this order.

Check for a typo. Report numbers are long. Re transcribe it.

Check you are using the right laboratory's database. A GIA number will not resolve on IGI's site and vice versa.

Check it is a diamond report and not one for a different material. Moissanite is not graded by IGI in the same way. Ours is GRC certified, a separate system with its own verification.

Ask the retailer for the number in writing. If they hesitate, that is your answer. A grading report is not confidential information.

If it still does not resolve and the seller cannot explain why, walk away. There is no scenario where an unverifiable certificate is a good sign, and no shortage of stones with reports that check out. The point of independent grading is that you do not have to take anyone's word for anything.

What the certificate does not tell you

This is the part most guides leave out, and it matters more than the field by field reading above.

It does not tell you how the stone looks. A report is measurements and grades, not a photograph and not a judgement about beauty. Two stones with identical reports, same carat, colour, clarity and cut grade, can look meaningfully different in the hand, because grade bands are ranges and things like the exact facet pattern and the extent of a cloud sit inside those ranges. Look at the stone, or at video of the actual stone, before you decide.

It does not tell you about the setting or the workmanship. Nothing on that page describes the ring. Not the claw thickness, not the shank at the base, not whether the casting was properly finished, not whether the setter actually tightened the claws, not who made it or what happens when something moves. The setting is what fails. A perfect certificate has never stopped a stone falling out of a badly made head.

It is not a valuation. A grading report contains no price. An insurance valuation is a different document for a different purpose, and neither tells you what anyone would pay you for the ring.

It does not make a stone a good buy. Grades are a negotiation. I would rather sell you a G colour, VS2, excellent cut stone with its inclusion tucked under a claw than a D VVS1 that costs considerably more and looks the same on a hand.

Use the report to verify. Use your eyes to choose. If it helps to see how lab grown and mined stones compare on grading and price, the lab grown versus mined comparison sets both out side by side, and every stone in the lab grown diamond engagement rings collection comes with its IGI report and its inscription.

Common questions

Are lab grown diamonds GIA certified?

They can be. GIA now issues full grading reports for lab grown diamonds. Most lab grown stones on the market carry IGI reports instead, because IGI graded the category first and the supply chain standardised around it.

Is IGI as reliable as GIA?

Both are established laboratories issuing detailed reports. GIA has a longer reputation in mined diamond grading and applies its scale strictly. Any two laboratories can differ by a grade on colour or clarity, so compare stones graded by the same laboratory when you are comparing closely, and judge the stone itself rather than the letterhead.

Where is the IGI number on a diamond?

Laser inscribed on the girdle, which is the thin band around the widest part of the stone. It needs magnification to read. Ask your jeweller to show you.

Does every lab grown diamond come with a certificate?

It should. Small accent stones often do not, because grading costs more than the stone is worth, but any centre stone should carry a report with a verifiable number.

Does a certificate mean the ring is well made?

No. The report describes the stone only. It says nothing about the setting, the claws, the casting or the finishing, and those are the parts that fail with wear.