Lab-Grown Diamond Certification: What to Check on the Report
GIA stopped full 4Cs grading on lab-grown diamonds in October 2025; IGI still does. What that split means, and exactly what to check before you buy.
A lab-grown diamond needs independent certification just as much as a natural one does — but as of late 2025, the two major labs no longer grade lab-grown stones the same way, and it's worth knowing why before you read a report.
GIA's October 2025 change
Since 1 October 2025, GIA no longer issues traditional 4Cs colour-and-clarity grades on laboratory-grown diamonds. Instead it uses a two-tier descriptive system: a stone is classed as either "premium" (broadly near-colourless, D-F equivalent colour, VVS-VS equivalent clarity, excellent finish) or "standard" (roughly G-J equivalent colour, clarity that may fall into the SI range, good but not top-tier finish). GIA's stated reason is that over 95% of lab-grown production now clusters tightly at the high end of colour and clarity, making the fine-grained scale built for natural diamond's much wider spread less meaningful for lab-grown. Natural diamonds are unaffected — they still receive full traditional grading.
IGI still grades lab-grown on the full scale
IGI continues to issue full 4Cs colour and clarity grades on lab-grown diamonds, which is a significant part of why most lab-grown diamonds on the market today ship with an IGI report rather than a GIA one — it's the more directly comparable report if you're weighing a lab-grown stone against natural diamond grades you already understand.
What to check on either report
- "Laboratory-grown" stated explicitly — never buy a stone without this confirmed in writing.
- Growth method disclosed — a good report notes CVD or HPHT (see our CVD vs HPHT guide).
- Post-growth treatment disclosed — HPHT colour-annealing after CVD growth is common and must be stated, not left implied.
- Girdle laser inscription present and matching the report number — the practical way anyone, not just a lab, can verify the stone against its paperwork (see can jewellers tell lab-grown apart).
- Which grading system was used — GIA's premium/standard tiers and IGI's full 4Cs aren't directly interchangeable; know which you're reading before comparing two stones across labs.
Related reading
- Lab-grown vs natural diamonds: what buyers need to know
- Which cert lab to trust
- Is a lab-grown diamond worth it?
Sources: GIA's announced grading change, effective 1 October 2025, and IGI's published lab-grown reporting practice (igi.org).
CVD vs HPHT Lab-Grown Diamonds: What's the Difference?
The two processes used to grow diamonds in a lab produce real diamonds by different routes — and the difference shows up in typical colour, clarity and price.
Can Jewellers Tell If a Diamond Is Lab-Grown?
Not by eye, and not with a loupe — lab-grown and natural diamonds are optically identical. What actually detects the difference, and why a report beats an opinion.
Do Lab-Grown Diamonds Hold Their Value?
No — and it's structural, not incidental. Why lab-grown diamond prices have kept falling since large-scale production began, and what that means for resale.
Compare real stones before you commit
Use Chaos to understand certificates, pricing, availability and dealer supply before asking for a specific stone.