Why GIA Stopped Grading Lab-Grown Diamonds on the 4Cs Scale

GIA announced in October 2024 that lab-grown diamonds submitted from that point would no longer receive the standard 4Cs colour and clarity grades¹. The new format is a two-tier quality assessment: Premium or Standard. Stones whose quality falls below the Standard threshold are not issued a report at all.

The change applies only to GIA reports issued from October 2024 onward. Pre-existing GIA reports for lab-grown diamonds remain valid. They continue to display the traditional Cut, Colour, Clarity, and Carat grades, and are unaffected by the new format. The change does not apply to natural diamond grading; D-Z and FL-I3 scales remain in use for mined stones⁶.

Other laboratories did not adopt the change. IGI, GCAL, GSI, and other graders continue to use the 4Cs framework for lab-grown diamonds. A buyer comparing reports from October 2024 onward may therefore see GIA showing Premium or Standard, and IGI showing, for example, F VS1.

GIA's stated reasoning was twofold. First, the population of laboratory-grown diamonds clusters tightly across the colour and clarity continuum¹. The laboratory's analysis of grading data found that more than ninety-five per cent of submitted lab-grown stones fall within a narrow band of grades, far narrower than the natural diamond population. A scale designed to span a wide range provides less practical information when applied to a narrowly distributed sample.

Second, GIA expressed concern that consumers were over-relying on small grade differences in lab-grown stones in a way that did not reflect their actual visual or quality differences. A G colour CVD-grown stone and an H colour CVD-grown stone are far closer to each other than the same colour pair would be for natural stones, because both come from the same narrow tail of the lab-grown distribution. The Premium / Standard binary acknowledges that.

Trade press has also pointed to a less explicit consequence. The 4Cs framework makes grade-by-grade price comparison straightforward, which intensifies competition and downward price pressure. A Premium / Standard binary aggregates fine-grained grades into broader tiers, which slows comparison shopping and softens grade-step price compression. GIA itself has not framed the change in these terms, but industry commentators have³⁵.

The initial October 2024 announcement provoked a strong reaction from parts of the industry, particularly from retailers and producers who had built marketing around colour and clarity grades. GIA subsequently clarified some terminology and provided additional guidance about how the new tiers map to the old grades³⁴.

The clarifications did not reverse the format change. New GIA lab-grown reports continue to use Premium / Standard. What changed in the follow-up communications was the explanatory framing: GIA emphasised that the new format remains a rigorous quality assessment, that the underlying grading work continues to use the same gemmological methods, and that the new format is intended to better serve consumers who look at the report rather than to deprive them of detail.

For a buyer holding a pre-October-2024 GIA-graded lab-grown report: nothing changes. The report continues to describe the stone as it did when issued. The 4Cs grades remain on the document.

For a buyer choosing a stone after October 2024 with a GIA report: the report shows Premium or Standard rather than letter and inclusion grades. Comparison across stones is binary at the GIA-side, finer-grained on the IGI-side, and impossible to align directly. Trade-press buying guidance has converged on three patterns: (1) compare like-for-like by laboratory, (2) ask for the stone in person under controlled lighting if precision matters, and (3) accept that the GIA report is now telling you the stone clears a quality threshold rather than placing it on a spectrum.

For the trade, the change has implications for inventory management and pricing. A retailer selling lab-grown stones with new GIA reports cannot quote a colour-and-clarity-anchored price; the report does not contain those grades. The retailer either commissions an IGI report alongside the GIA report, or prices on a Premium / Standard basis. Both approaches are now being tried.

The change does not occur in isolation. It coincides with several other industry events: the De Beers Lightbox brand cut its prices to five hundred dollars per carat in 2024, then announced closure in 2025; Bain's Global Diamond Industry Report tracked continued lab-grown wholesale price decline; and AWDC reported sharp Q1 2026 weakness in rough diamond prices. The full timeline is in Chapter 8.

Whether the GIA grading change will, in aggregate, slow lab-grown wholesale price decline is an open question. The mechanics suggest it could: by removing fine-grained comparison points from the most-prestigious lab-grown reports, the change makes some price pressure harder to express. The counterforce is that IGI and other laboratories continue to use the 4Cs scales for lab-grown stones, and most lab-grown grading volume is now on IGI reports.

Where this fits in the reference

This chapter sits between Chapter 4 (GIA vs IGI) and Chapter 6 (FTC Diamond Rules). The grading change is a private-sector decision; the FTC rules are the public regulatory framework. Both shape what consumers see at retail. Chapter 7 explores how grading granularity intersects with the lab-grown price structure.