What is the difference between GIA, IGI and in-house reports for lab-grown diamonds?

ZKZ Editorial TeamMain answer · Product & gemmology desk

GIA and IGI are independent laboratories that issue reports on lab-grown diamonds, but they describe quality in different ways, and an in-house report comes from the seller, so it is not independent. Compare reports from the same laboratory when you can, and verify the number with the issuer.

What we verified

Fact GIA says that from 1 October 2025 its Laboratory-Grown Diamond Quality Assessment classifies stones as Premium or Standard based on overall clarity, colour and cut rather than using the nomenclature developed for natural diamonds, and that stones not meeting the minimum for Standard receive no assessment.

Fact GIA says it also offers a Laboratory-Grown Diamond Report – Dossier, for stones up to 9.99 carats in most locations, from which growth type and post-growth treatment options were removed.

Fact IGI says its lab-grown diamond reports use a colour scale from D to Z and clarity grades from IF to I3, assess cut for round brilliants against its own studies, and note polish and symmetry, and that it notes the growth process and treatments in the comments upon request.

Fact IGI says its report is an opinion and should not be relied on as a guarantee, appraisal or warranty, and that opinions from laboratories may vary.

How to compare

Our advice Verify the report number on the laboratory's own site, and check that the inscription and measurements match.

Our advice Treat an in-house report as the seller's description, and ask for an independent one if the price is high.

It depends Which laboratory is better is a matter of debate, and we do not rank them.

Questions to ask before you pay

• Which laboratory issued the report, and what type of report is it?
• Is the report number inscribed on the stone?
• Can I verify the report on the laboratory's website?
• Does the report state growth type and treatment?

Our advice Keep the report with your invoice and take photographs of the stone and any inscription.

Uncertain We did not verify how in-house reports are produced, or how the grades of the two laboratories compare in practice.

Related reading: What does fluorescence mean on a lab-grown diamond report? · Lab Grown Diamond Certification: IGI, GIA and What to Check

Sources

• GIA press release, updated laboratory-grown diamond services (2025)
• GIA, Laboratory-Grown Diamond Report Dossier FAQ
• IGI, Lab grown diamond reports
• IGI, Verify your report

Fact = stated by the cited source. Our advice = editorial recommendation. Uncertain / it depends = limits of what can be said in general.