IGI or GIA: which report should a lab-grown diamond have?
IGI (International Gemological Institute) certification is legitimate, and IGI is the choice for most buyers who want a full grade: since 1 October 2025 GIA (Gemological Institute of America) no longer grades lab-grown diamonds on its D-to-Z colour and FL-to-I3 clarity scales; it gives a "Premium" or "Standard" designation, or no assessment if the stone falls below Standard, while an IGI report still gives full colour, clarity and cut grades. Whichever you have, look the number up yourself and check that it matches the stone.
What each report gives you
Both laboratories examine the stone itself and file the result under a number you can look up. An IGI lab-grown report records shape, weight, colour and clarity grades, cut, measurements and that the stone is laboratory-grown. A GIA lab-grown assessment issued since 1 October 2025 says the stone is laboratory-grown and whether it is "Premium" (D colour, VVS clarity or better, Excellent polish and symmetry) or "Standard" (E to J colour, VS clarity or better, Very Good polish and symmetry, or Good symmetry on fancy shapes); a stone below Standard gets no GIA assessment. GIA reports for lab-grown diamonds issued before the change remain valid.
What is not a substitute
A certificate printed by the seller, a "GRA" card, or an "appraisal" that states a replacement value but no measurements. None of them is an independent examination you can verify.
How to use it on Amazon
Prefer listings that show the laboratory and the report number up front. Look the number up before buying, compare the measurements, and have an appraiser read the girdle inscription when it arrives.
| IGI lab-grown report | GIA lab-grown assessment (since 1 October 2025) | |
|---|---|---|
| What the laboratory is | A for-profit company | A nonprofit institute |
| Colour and clarity | Full grades | No grades: "Premium" (D colour, VVS or better) or "Standard" (E to J, VS or better); below Standard, no assessment |
| Cut grade on round brilliants | Cut is graded | Premium: "Cut grade – Excellent (round brilliant cut diamonds only)". Standard: "Cut grade – Very Good (round brilliant cut diamonds only)" |
| Growth method | Stated on the report (CVD or HPHT), with any post-growth treatment | Not stated in GIA's announcement |
| Girdle inscription | Usually "LG" followed by the report number | "Laboratory-Grown" and the GIA quality assessment number |
| Where to look it up | Report verification on igi.org | Report Check on gia.edu |
Frequently Asked Questions
Are IGI grades softer than GIA grades?
Buyers and dealers often say so, especially for mined diamonds. For lab-grown diamonds the comparison has changed: since 1 October 2025 GIA gives lab-grown stones a "Premium" or "Standard" designation instead of colour and clarity grades, so only IGI's report gives the letters. Judge the stone and the measurements, not only the grades.
Is an older GIA report on a lab-grown diamond still valid?
Yes. GIA says existing GIA reports for laboratory-grown diamonds remain valid, so a report issued before the change, with colour and clarity grades, still stands. Look the number up on gia.edu as usual.
Sources
- GIA: Updated laboratory-grown diamond services to launch October 1 (26 August 2025)
- GIA: New descriptive terminology for laboratory-grown diamonds (2 June 2025)
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