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 and issues detailed reports for loose stones and finished jewelry. At Signora, each selected individual lab-grown center or primary diamond of 0.50 ct or larger includes an independent IGI grading report. The product page states whether the document covers an individual stone or a complete finished piece.

An IGI report is a professional grading opinion. Trained gemologists examine the stone or finished piece identified by the report under standardized conditions and record their findings. Reports help comparison, but grading remains expert opinion and report formats and scope vary.

Just as important is what the report is not:

• It is not a price tag. A grading report does not state market or replacement value.
• It is not an appraisal. An appraisal is a separate document that assigns a replacement value for insurance.
• It is not a beauty score. Two stones with similar grades can face up differently.
• It is not infallible. Color and clarity grading involves expert judgment, and small differences of opinion between laboratories are possible.

The layout and fields depend on whether the document is a loose-stone grading report, an identification report or a finished-jewelry report. A loose-diamond grading report commonly records:

• Report number and date — the identifier used for online verification.
• Shape and cutting style.
• Measurements and carat weight.
• Color and clarity grades.
• Cut, polish, symmetry and fluorescence where applicable to that report type.

Always read the title and scope on the exact document supplied. If a line is unclear, send us a photo and we will walk you through it.

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 and description identify the documented stone as lab-grown. When the exact report also confirms a girdle inscription, that inscription can support a match to the documented stone. 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 diamond seed to finished stone, our From Seed to Signora 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.

For an IGI document that supports online verification:

1. Find the report number on the document.
2. Go to igi.org and open the report verification page.
3. Enter the number and compare the online record with the supplied document.
4. Compare the reported measurements and other applicable fields with the item.

A girdle inscription or QR code may be present when the exact report confirms it; do not assume either for a finished-jewelry report or an uninscribed stone. If any record disagrees, stop and ask Signora before relying on it.

When the exact IGI report confirms a girdle inscription, its number can be compared with the supplied report. Do not assume an inscription from carat weight alone. A finished-jewelry report has a different scope and does not, by itself, establish a separate inscription for stones not individually listed on that report.

A jeweler can locate a stated inscription under magnification and compare it with the report number. If a setting hides it or you cannot confirm it, contact Signora with the order and report details.

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.

IGI became a high-volume standard for lab-grown diamonds and issues reports for loose stones and finished jewelry. GIA also grades lab-grown diamonds.

Both labs use established grading scales. Our advice is to judge the individual stone and the exact report supplied for it, not the logo alone. Signora states the lab, report type and scope on the product page or in the approved custom specification. 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 report is issued by an independent laboratory and records the laboratory's grading or identification opinion, including the fields applicable to that report's stated scope. It contains no price and is tied to the item and condition it documents. An appraisal is issued by a jewelry appraiser and states a replacement value in currency — a figure an insurer may use to set a premium and settle a claim. The appraiser evaluates the item and available records, then adds a market valuation that can change over time.

You may need both when a grading report is supplied: the report to understand the laboratory record, and the appraisal if your insurer requires a replacement value. The comparison table below puts them side by side, and our jewelry insurance guide explains the process.

Every finished piece includes a Signora Jewelry Certificate recording the piece and selected materials; gold purity is independently tested by an external body. Each approved individual lab-grown center or primary diamond of 0.50 ct or more includes an independent IGI grading report. For diamonds below 0.50 ct, moissanite, gemstones and other stones, independent documentation is included only when the product page or approved specification states the laboratory, report type and scope.

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

• Store the supplied documentation with your receipt — together they record what you own and what you paid.
• Photograph both and keep the images somewhere backed up, alongside a photo of the piece itself.
• Verify a laboratory report through the issuing lab using its report number.
• If paper documentation goes missing, our client care team can help from our side with your order details.