What Certification Should a Lab Grown Diamond Have in 2026?

In 2026, IGI (International Gemological Institute) is the right certification for most lab grown diamond buyers. It holds roughly 65% of the global lab grown diamond certification market, issues full 4Cs letter grades, and discloses the growth method on every report. GIA is a credible institution, but since October 2025 it no longer assigns individual color and clarity grades to lab grown diamonds, which limits how useful its reports are when you are comparing stones side by side.

That shift matters more than it might sound. If you are spending $500 or $5,000 on a lab grown diamond, you want to know whether you are buying an F VS1 or a G SI2. Under the new GIA system, you may not get that answer. This article explains why the certification gap opened, what a legitimate report must include regardless of which lab issues it, and how to read that document before you buy.

loose stone Why did GIA change its lab grown diamond grading in 2025?

On October 1, 2025, GIA replaced its full 4Cs grading for lab grown diamonds with a simplified two-tier quality assessment. A stone now receives either a “Premium” or “Standard” designation based on a combined read of color, clarity, and cut. Stones that fall below the Standard threshold receive no assessment at all.

The criteria are narrow. To earn Premium, a diamond must be D color, VVS clarity or higher, with Excellent polish and symmetry. Standard covers stones with at least VS clarity, E-to-J color, and Very Good polish. GIA’s reasoning, stated publicly, is that over 95% of lab-grown diamonds now cluster between D and F color with VVS to VS clarity, making the full letter-grade scale less meaningful for manufactured stones.

The practical consequence is that two stones with meaningfully different quality profiles can both receive the same “Standard” label. A G-VS2 and a J-SI1 are not the same diamond, but a GIA report issued after October 2025 may not tell you which one you are holding. Reports issued before the October 2025 cutoff still carry the old full 4Cs grades and remain valid.

Why does IGI dominate lab grown diamond certification?

IGI entered the lab grown diamond market earlier than most grading labs, built out a network of more than 30 laboratories across multiple countries, and kept certification costs lower than competitors. That combination compounded over time. By the time IGI filed its IPO prospectus in 2024, the company estimated it held approximately 65% of the global laboratory grown diamond certification market. Trade data from online diamond marketplaces in 2026 puts IGI’s share of listed lab grown inventory at roughly two-thirds of all lab grown stones.

The report itself is the practical reason buyers and retailers keep choosing IGI. It still issues a complete 4Cs grading: a specific color grade (D through Z), a clarity grade (Flawless through I3), a cut grade for round brilliants, plus polish and symmetry. It also records fluorescence, exact measurements, and the growth method. That level of detail lets you compare two stones on a spreadsheet and make a rational decision. A broad “Premium” label does not.

For buyers working with a store like Dvik Jewels, which selects IGI-and GIA certified stones specifically for quality and authenticity, the IGI report is the document that makes the stone’s grade verifiable and the price defensible.

What must a legitimate lab grown diamond certificate include?

Certification format matters less than certification content. Whether the report comes from IGI or any other recognized lab, these fields must be present before you consider a purchase.

The 4Cs with specific grades. Cut, color, clarity, and carat weight should each appear as a discrete grade, not a combined descriptor. This is the primary reason an IGI report currently gives buyers more actionable information than a post-October 2025 GIA assessment for lab grown stones.

Growth method disclosure. The certificate must state whether the diamond was grown by CVD (Chemical Vapor Deposition) or HPHT (High Pressure High Temperature). Both methods produce real diamonds with identical physical and chemical properties to mined stones, but the disclosure is a standard part of any credible lab grown report and confirms the stone’s origin.

A laser inscription and a verifiable report number. IGI inscribes its report number on the diamond’s girdle, typically with an LG prefix for lab grown stones. You can confirm the inscription under 10x magnification and then cross-check it against the grading data at igi.org. If the number on the stone and the number on the paper do not match, stop the transaction. A certificate without a verifiable report number is not a certificate.

Origin confirmation. The report should explicitly state “Laboratory Grown.” This is not a formality. It is the document’s legal and commercial declaration that the stone is not a mined diamond.

Are there other certification labs worth considering?

IGI and GIA together account for roughly 80% of the global diamond certification market, so most stones you encounter will carry one of those two reports. A few other labs appear in the market, including GCAL (Gem Certification and Assurance Lab), which is US-based and well regarded for its light performance grading, and AGS (American Gem Society), though AGS merged its operations with GCAL in 2023.

For most buyers in the US, an IGI certificate is what you will find on the overwhelming majority of lab grown diamonds sold online and in stores. If a seller presents a report from a lab you cannot independently verify at the lab’s own website, that is a reason to ask questions before proceeding.

IGI Certification Gives You the Most Useful Data

The certification question for lab grown diamonds in 2026 has a clear answer: IGI. GIA remains a respected institution for diamond quality  , but its October 2025 decision to replace full 4Cs grading with broad Premium and Standard tiers means its lab grown reports no longer give buyers the grade-by-grade detail needed to compare stones confidently. IGI continues to issue complete 4Cs reports, discloses the growth method, and provides a verifiable laser inscription on every stone. Those three things, taken together, are what certification is supposed to do.

If you are shopping for a lab grown diamond engagement ring or any certified loose stone, ask to see the full report before you buy. The certificate number should match the girdle inscription, the growth method should be stated, and the 4Cs should appear as individual grades, not a single tier.certified stones 

FAQs

1. Can I trust a lab grown diamond with only a seller’s in-house grading certificate?

No. In-house grading is not independent verification. A legitimate lab grown diamond should come with a report from a recognized third-party lab such as IGI, GIA, or GCAL. Without independent grading, there is no objective way to confirm the stated color, clarity, or carat weight, and the stone’s resale or trade-in value will be significantly harder to establish.

2. Does the growth method on a certificate (CVD vs. HPHT) affect diamond quality?

Not in D color, VVS clarity any way that matters to most buyers. Both CVD and HPHT produce diamonds with the same physical and optical properties as mined stones. The disclosure exists for transparency, not because one method produces a better gem. A well-cut, well-graded CVD diamond and a well-cut, well-graded HPHT stone are functionally identical in appearance and durability.

3. If I have a GIA lab grown diamond graded before October 2025, is my old report still valid?

Yes. GIA confirmed that reports issued before October 1, 2025 are unaffected by the format change. If your diamond carries a GIA report showing specific D-to-Z color and FL-to-I3 clarity grades, those grades stand. The new Premium and Standard system applies only to diamonds submitted to GIA from October 2025 onward.

4. How do I verify an IGI certificate is real and has not been altered?

Go to igi.org, enter the report number printed on the certificate, and compare every field on screen against the physical document. Then ask to see the diamond’s girdle under magnification and confirm that the laser-inscribed number matches. Any discrepancy between the inscription and the printed report number is a red flag worth investigating before completing the purchase.

5. Does IGI grading strictness compare well to GIA for lab grown diamonds?

GIA is generally considered slightly more conservative on color grading, with a gap of roughly one grade on color being common between the two labs for equivalent stones. That means an IGI G-color stone might grade closer to H under GIA’s scale. For lab grown diamonds, where price per carat is already significantly lower than mined