IGI Diamond Certification Guide

IGI — the International Gemological Institute — is one of the world's largest independent gemological laboratories. Founded in Antwerp in 1975, it now operates grading labs across the major diamond centers, including Antwerp, New York, Mumbai and Surat, the city where every Signora piece is made. IGI grades loose diamonds, colored stones and finished jewelry, and it does not buy or sell any of them — which is the whole point. A grading lab only works if it has nothing to gain from the grade.

IGI matters especially for lab-grown diamonds because it committed to them early. While much of the industry hesitated, IGI issued full grading reports for lab-grown stones — the same color, clarity and cut analysis a mined diamond receives — and built the capacity to do it at scale. Today the majority of certified lab-grown diamonds on the market carry IGI paperwork, which is why the IGI report has become the working standard for the category. Every lab-grown diamond Signora sets ships with one.

An IGI report is a professional grading opinion. Trained gemologists examine your stone under standardized lighting and instruments, compare it against master stones, and record what they find in consistent language. Because the lab is independent of the seller, the report lets you compare diamonds honestly — a VS1 on one report means the same thing as a VS1 on another.

Just as important is what the report is not:

• It is not a price tag. No IGI report states what a diamond is worth, and it never will. Value is set by the market; the report only describes quality.
• It is not an appraisal. An appraisal is a separate document that assigns a replacement value for insurance — more on that below.
• It is not a beauty score. Two stones with identical grades can face up differently. Grades describe measurable quality; your eye judges the rest.
• It is not infallible. Color and clarity grading involves expert human judgment. Reputable labs are consistent, but a one-grade difference of opinion between labs is possible and normal.

The layout varies slightly by report type, but every IGI diamond report covers the same core facts:

• Report number and date — the unique ID that ties this document to your stone, and your key to online verification.
• Shape and cutting style — for example, round brilliant or emerald step cut.
• Measurements — the stone's dimensions in millimeters, precise to a hundredth.
• Carat weight — measured, not estimated, to two decimal places.
• Color grade — on the D-to-Z scale, where D is colorless and warmth increases down the alphabet.
• Clarity grade — from Flawless to Included, based on what a grader finds under 10x magnification.
• Cut grade — for round brilliants, an overall assessment of proportions; fancy shapes list proportion details instead.
• Polish and symmetry — how finely the facets are finished and how precisely they align.
• Fluorescence — how the stone reacts to UV light, from None to Strong. In lab-grown diamonds it is usually None.

If a line on your report is unclear, send us a photo of it — we will happily walk you through your own certificate.

An IGI lab-grown report carries a few lines a mined-diamond report does not, and they are worth understanding.

The report says "laboratory grown" plainly. There is no ambiguity: the report type, the description and the inscription all identify the stone as lab-grown. Honest disclosure is the foundation of the category.

Growth method: CVD or HPHT. These are the two ways science grows a diamond — Chemical Vapor Deposition builds the crystal atom by atom from carbon-rich gas, while High Pressure High Temperature recreates the conditions of the Earth's mantle. Both produce real diamonds with the same crystal structure, and neither is graded more favorably than the other. If you want the full journey from carbon seed to finished stone, our Grown, Not Mined page tells it properly.

Treatment comments. Some lab-grown diamonds receive post-growth treatment — typically HPHT annealing to refine color. IGI discloses this in the comments: a stone may read "as grown" or note treatment. Post-growth treatment is common, stable and permanent; the disclosure exists so you know exactly what you own, not because anything is wrong with the stone.

Every IGI report can be checked against the lab's own database in about a minute:

1. Find the report number on your certificate — it also appears on the stone's girdle inscription.
2. Go to igi.org and open the report verification page.
3. Enter the number. IGI displays the report's details — shape, carat weight, color, clarity and the rest.
4. Compare what is on screen with what is on paper, and with the stone itself. Carat weight and measurements should match exactly.

Newer IGI reports also carry a QR code that opens the digital record directly from your phone. If the online record ever disagrees with the paper in your hand, stop and ask questions — of any seller, including us. That is exactly what verification is for. It also means the certificate is never truly lost: the record lives with the lab, not just in your drawer.

A certificate describes a diamond, but how do you know it describes your diamond? The answer sits on the girdle — the thin outer edge of the stone. IGI laser-inscribes the report number onto the girdle of the lab-grown diamonds it certifies, in characters far too small to see unaided and too shallow to affect the stone in any way. Lab-grown inscriptions also identify the stone as lab-grown alongside the number.

To find it, use a 10x jeweler's loupe under bright light and rotate the stone slowly, watching the girdle edge. Be patient — the inscription occupies a tiny arc, and in a finished ring it can hide behind a prong. If you cannot find it yourself, any local jeweler with a microscope can locate it in moments, or you can send us a note and we will tell you where to look on your particular setting.

When the number on the girdle matches the number on the report, the match is closed: this stone, this paper, no substitution possible. It is the simplest anti-mix-up mechanism in the industry, and one more reason certification beats reassurance.

Ask about diamond certification and the two names you will hear are IGI and GIA. Both are respected, independent laboratories, and neither deserves the tribal loyalty the internet sometimes gives them.

GIA — the Gemological Institute of America, founded in 1931 — created the 4Cs and the D-to-Z color scale the whole industry uses. It carries enormous historic authority, particularly in natural diamonds, where its reports have long been the reference point.

IGI became the high-volume standard for lab-grown diamonds. It graded lab-grown stones with full, specific reports years before most of the industry, and today grades the majority of certified lab-grown diamonds sold worldwide. GIA now issues specific grades for lab-grown too, but IGI's head start means most lab-grown inventory — including ours — carries IGI paperwork.

Both labs grade on the same scales, so the reports read the same way. Our honest advice: for a lab-grown diamond, an IGI report is the normal, credible standard — judge the stone and its grades, not the logo on the folder. Signora's lab-grown diamonds are IGI-certified; if you commission a natural stone by special request, certification options are part of that conversation with the atelier. For the deeper mined-versus-grown question, see our lab-grown vs natural guide.

These two documents are confused constantly, and the confusion costs people money. A grading certificate is issued by an independent laboratory and describes quality: carat, color, clarity, cut. It contains no price and never expires, because the stone it describes does not change. An appraisal is issued by a jewelry appraiser and states a replacement value in currency — the figure an insurer uses to set your premium and settle a claim. It relies on the certificate for the stone's facts, then adds a market valuation that can and does change over time.

You may need both: the certificate to know what you own, the appraisal to insure it. The comparison table below puts them side by side, and our jewelry insurance guide covers how to turn one into the other without overpaying for cover.

Certification at Signora is not an upgrade or an option. Every lab-grown diamond we set ships IGI-certified, every moissanite ships GRA-certified, and the certificate travels in the box with your piece — nothing to request, nothing extra to pay. The grades themselves are held to a fixed floor we publish openly: The Signora Standard explains exactly what every stone meets or exceeds, so the certificate confirms a promise rather than revealing a surprise.

Once the box is open, treat the paperwork as part of the piece:

• Store the certificate with your receipt — together they document what you own and what you paid, which is precisely what an insurer will ask for.
• Photograph both and keep the images somewhere backed up, alongside a photo of the piece itself.
• Verify the report once at igi.org when your piece arrives, so you have seen the online record yourself.
• If the paper ever goes missing, the record survives at the lab — and our client care team can help from our side with your order details.