What Is IGI Certification? And Why It Matters for Your Diamond

IGI (the International Gemological Institute) is an independent laboratory that grades and certifies diamonds, issuing a report that documents a stone's 4Cs, precise measurements, proportions and whether it is lab-grown or mined. For lab-grown diamonds it is the leading global benchmark, and every Signora diamond ships with its own IGI certificate.

What exactly is IGI certification?

IGI is a third-party gemological laboratory founded in 1975, with grading offices across the world. It has no stake in whether you buy a particular stone, which is precisely the point: an IGI report is an unbiased, expert opinion on what a diamond actually is.

An IGI certified diamond has been examined by trained gemologists using calibrated instruments rather than a salesperson's eye. The result is a written report, sometimes called a grading certificate or dossier, that travels with the stone for life. It is not an appraisal of dollar value, it is a description of physical facts.

That distinction matters. Two diamonds can look identical in a photo and be priced hundreds of dollars apart. The certificate is how you tell whether the difference is real quality or just marketing.

What does an IGI report actually show?

An IGI report is denser than most people expect. Read past the headline grades and you will find a full technical profile of the stone.

• The 4Cs: carat weight, color grade, clarity grade and cut quality, the four factors that drive most of a diamond's price. If these are new to you, our guide to the 4Cs of diamonds breaks each one down.
• Exact measurements: length, width and depth in millimeters, so you know the physical size, not just the carat weight.
• Proportions: table percentage, depth percentage, crown and pavilion angles, girdle and culet, the numbers that determine how much a stone sparkles.
• Finish grades: polish and symmetry, which describe how well the diamond was cut and finished.
• Fluorescence: whether the stone glows under UV light, and how strongly.
• Origin statement: a clear line identifying the diamond as laboratory-grown, along with the growth method.

Many reports also include a plotted clarity diagram mapping the location of any inclusions, plus a unique report number you can verify on IGI's website.

Why is IGI the benchmark for lab-grown diamonds?

IGI was an early and consistent grader of laboratory-grown diamonds, and it built the reporting standards that the trade now leans on. Today the large majority of lab-grown diamonds sold worldwide carry an IGI report, which makes cross-shopping straightforward: an IGI G VS1 from one seller is graded on the same scale as an IGI G VS1 from another.

Crucially, IGI reports explicitly state that a stone is lab-grown and often laser-inscribe that fact, along with the report number, on the diamond's girdle. There is no ambiguity and nothing hidden. If you want the fuller picture on how these stones are made and why they are chemically identical to mined diamonds, see our guide to whether lab-grown diamonds are real.

Is an IGI lab-grown diamond a "real" diamond?

Yes. A lab-grown diamond is genuine diamond, the same carbon crystal as one pulled from the earth, with the same hardness, brilliance and fire. It is not a simulant like cubic zirconia or moissanite. The only real difference is origin: one grew over weeks in a controlled reactor, the other over billions of years underground.

Because the material is identical, an IGI certified diamond that is lab-grown will test as diamond on a standard thermal diamond tester. The report simply documents where it came from. This is also why a lab-grown stone can cost roughly 80 to 95 percent less than a mined diamond of the same certified quality, you are paying for the crystal, not the geology.

How do I read and verify an IGI certificate?

Start with the report number, then head to IGI's official verification page and type it in. The details on screen should match your printed or digital report exactly, from carat weight to clarity grade. If anything differs, stop and ask questions.

Next, check the laser inscription. Under magnification, the diamond's girdle should carry the same report number shown on the certificate, which links that specific stone to that specific document. Then read the grades in plain terms: color runs D (colorless) toward Z (light yellow), and clarity runs from Flawless down through the SI and I grades based on inclusions.

You do not need to chase the top of every scale. A near-colorless G or H with a VS clarity and an excellent cut usually looks stunning to the naked eye and stretches your budget far further than obsessing over a flawless D.

How does IGI certification protect my purchase?

A certificate is your receipt for quality. It lets you comparison-shop honestly, insure the piece for the correct value, and resell or upgrade later with proof of exactly what you own. Without one, you are trusting a seller's word on grades you cannot see.

At Signora, certification is standard rather than an upsell. Every diamond we set, whether it anchors one of our engagement rings or a pendant from our necklaces, arrives with its IGI report. You can also browse certified stones directly in our diamond finder and see the grades before you ever commit, with each ring made to order in solid gold or platinum.

The bottom line

IGI certification turns a diamond from a leap of faith into an informed choice. It documents the 4Cs, the exact measurements and proportions, and states plainly that a stone is lab-grown, all verified by an independent lab rather than the person selling it. Insist on it, learn to read it, and you will never overpay for a grade you cannot confirm. Ready to see certification in action? Explore our IGI-certified loose diamonds and choose your stone with the full report in hand.