Quality and Grading of Synthetic Diamonds
The fact that a diamond is synthetic (laboratory-grown) does not automatically reveal whether it is beautiful, well cut, free of visible inclusions, transparent, or desirable in the market. Origin and quality are different axes.
Synthetic diamonds may differ in weight, dimensions, color, clarity, transparency, cut, polish, symmetry, and luminescence. In 2026, however, laboratories do not all describe these differences using the same reporting system.
Five Separate Questions
For a synthetic product, it is useful to ask in sequence:
- Is the material diamond?
- Is its origin natural or synthetic?
- If it is synthetic, what is the growth method, and is there any post-growth treatment?
- What is the stone’s quality under the system of the particular laboratory?
- What is its market value in the specific channel and on the specific date?
A report may answer some of these questions, but not all of them.
The 4Cs as a Description of Properties
The carat is a unit of mass regardless of origin. Color, clarity, and cut geometry are also genuine observational or measurable properties of a synthetic diamond. The 4Cs can therefore be applied conceptually to synthetic material.
A particular laboratory may, however, choose to use a different nomenclature system. The most important modern example is GIA’s shift in 2025.
GIA: Laboratory-Grown Diamond Quality Assessment
As of October 23, 2026, GIA does not issue a classic natural-diamond 4C grading report for loose colorless-to-near-colorless synthetic diamonds weighing 0.15 ct and above; this has been the case since October 1, 2025. Instead, it uses a Laboratory-Grown Diamond Quality Assessment with an overall classification of Premium or Standard.
To qualify as Premium, all Premium criteria must be met: D-equivalent color, VVS or higher clarity, Excellent polish and symmetry, and Excellent cut for a standard round brilliant.
Standard encompasses a combination of Premium and Standard criteria down to defined minimums: E–J color-equivalent, VS clarity, Very Good polish, Very Good symmetry for round shapes or Very Good or Good for fancy shapes, and Very Good cut for a standard round brilliant.
If any criterion falls below the Standard threshold, the stone does not receive a GIA Quality Assessment classification. This is not the same as saying that it “is not diamond” or has no commercial value.
GIA currently offers a separate Laboratory-Grown Colored Diamond Report, which includes a full quality assessment, clarity plot, and an assessment of growth type and post-growth treatment for colored synthetic diamonds. GIA’s D–Z and fancy-color services must therefore not be conflated.
An Older GIA Report Remains a Historical Document
Before October 2025, GIA used a different format and more traditional 4C nomenclature for synthetic diamonds. An older report is not thereby “invalidated”; it remains a document of the results and methodology at the time it was issued.
When comparing an old and a new GIA document, it is therefore incorrect to automatically map one nomenclature onto the other.
IGI: A Separate Current System
IGI continues to issue a Laboratory Grown Diamond Report using the D–Z color scale, clarity categories from Flawless/Internally Flawless through Included, and cut information. It uses overall cut grading for round brilliants, while for fancy shapes it provides its own multicomponent approach incorporating finish, proportions, shape-specific requirements, and an assessment of light return.
IGI also states that the growth process and treatment can be recorded in the comments upon request. This is not the same as GIA’s Premium/Standard system, and no informal crosswalk should be constructed between them.
HRD Antwerp: No Reports for Loose Synthetic Diamonds from 2026
On June 18, 2025, HRD Antwerp announced that from 2026 it no longer issues quality reports for loose synthetic diamonds intended for commercial use. In limited cases it still analyzes synthetic diamonds, but strictly for research purposes, and jewelry containing synthetic stones remains eligible for a report.
This, too, is an institutional model, not proof that one universal industry report format exists.
GCAL by Sarine: Additional Focus on Measurement and Light Performance
GCAL by Sarine issues synthetic certificates that may contain the 4Cs, growth method, and additional analyses of proportions, optical symmetry, and light performance. Its 8X concept is a proprietary system. Claims about its superiority, accuracy, or market distinction are treated in this book as company claims unless supported by independent evidence; the existence and description of the report product itself can be supported by the issuer’s official documentation. The system should not be mapped to GIA, IGI, or HRD grades as if the categories were identical.
ISO and CIBJO Are Not a Grading Crosswalk
ISO 24016:2020 concerns the grading of natural unmounted polished diamonds above 0.25 ct and must not be extended to synthetic diamonds. Terminology documents such as ISO 18323 and the CIBJO Diamond Blue Book address nomenclature and disclosure, but they do not create one universal synthetic grading report.
Growth Method, Treatment, and Quality Grade Are Not the Same Fields
CVD-grown, HPHT-grown, HPHT-treated, D-equivalent, VVS-equivalent, Premium, Standard, and Excellent describe different things. One stone may, for example, be CVD-grown, subsequently HPHT-treated, and of very high commercial quality. Another may be as-grown HPHT with weaker clarity or polish.
Quality must therefore not be inferred from the growth method.
Report, Inscription, and Physical Matching
A report number and QR code help locate the digital record. A laser inscription helps link the stone to the document. But an online record is not proof that the stone in hand is physically the same specimen.
Physical matching includes comparison of weight, dimensions, shape, inscription, clarity characteristics, and other relevant details. This applies to both natural and synthetic products.
How to Compare Two Synthetic Diamonds
First, determine whether they belong to the same product and report category. Then compare weight and dimensions, color in the language of the specific report, clarity and transparency, cut in the same shape context, and polish and symmetry. Only then does it make sense to compare price.
If the report formats differ, do not assume that identically named or similar-sounding categories are fully equivalent.
Chapter Summary
- Synthetic origin is not a quality grade.
- Carat, color, clarity, and geometry remain genuine properties of a synthetic diamond.
- In 2026, laboratories do not use a single report system for synthetic products.
- Since October 1, 2025, GIA has used Premium/Standard for applicable D–Z synthetic diamonds.
- GIA’s colored synthetic service is separate and retains a more detailed description of color and clarity.
- IGI continues to use detailed 4C nomenclature in its synthetic report.
- HRD Antwerp no longer issues reports for loose synthetic diamonds from 2026; jewelry containing synthetic stones remains eligible for a report.
- GCAL by Sarine has proprietary quality and light-performance elements.
- Constructing an informal crosswalk among different laboratory systems is not professional.
- ISO 24016 must not be applied to synthetic diamonds.
- Growth method, treatment status, and quality grade are separate pieces of information.
- A report and laser inscription help identification but do not replace physical matching of the stone.
Sources for this chapter
Sources are primary or authoritative; the label in brackets gives the jurisdiction or source type.
- GIA: Laboratory-Grown Diamond Services Details
- IGI: Lab Grown Diamond Report
- AWDC / HRD: World First: Antwerp Diamond Lab HRD Becomes First in the World to End Quality Certification for Loose Synthetic Diamonds (18 June 2025) (jurisdiction: Belgium)
- HRD: Diamond Grading Reports (jurisdiction: Belgium)
- ISO: ISO 18323:2015 (jurisdiction: international)
- ISO: ISO 24016:2020 (scope: natural) (jurisdiction: international)
- CIBJO: Diamond Blue Book 2026-1 (jurisdiction: international)