The CIBJO Diamond Commission has proposed that the 4Cs grading system should be used exclusively for natural diamonds and that “synthetic” should become the preferred term for diamonds produced through industrial processes.
The proposal is contained in the fourth pre-Congress Special Report ahead of the 2026 CIBJO Congress, scheduled to take place in Vicenza, Italy, from September 4. The report was prepared by the Diamond Commission, headed by Udi Sheintal.
Proposed Change to Terminology
The report calls for CIBJO to reconsider its terminology for synthetic diamonds, with “synthetic” proposed as the preferred term rather than “laboratory-grown” or “laboratory-created”.
CIBJO’s current Diamond Terminology Guideline permits “synthetic”, “laboratory-grown” and “laboratory-created” when describing synthetic diamonds. Its guidance also states that a diamond without a qualifying term refers to a natural diamond.
The proposed change would revise terminology adopted by CIBJO in 2010. Amendments to the Diamond Blue Book are due to be presented at the 2026 Congress for consideration and approval.
Why the 4Cs Are Being Reconsidered?
The report argues that the 4Cs, covering colour, clarity, cut and carat weight, were developed to communicate the characteristics and rarity of natural diamonds.
“The Diamond Commission should continue to explore every way possible to restrict the use of the 4Cs so that they refer only to natural diamonds,” writes Mr. Sheintal. “This is because it is a tool intended to define the rarity and uniqueness of natural stones, where each one is different from the other. We need to end the use of the 4Cs for grading synthetic diamonds, given that they are industrially produced. They should be subject to a specific quality-control nomenclature, which is suitable for man-made products.”
The report states that synthetic diamonds are produced under controlled manufacturing conditions, allowing producers to determine characteristics during production.
“When the 4Cs grading scale is used by the synthetic diamond industry to describe its production, the consumer is misled to believe that synthetic diamonds are rare like natural diamonds. This is clearly not the case, because the synthetic diamond manufacturer determines and controls the production parameters, with the objective of achieving predetermined quality characteristics,” Mr. Sheintal adds.
The report distinguishes the terminology debate from the question of whether synthetic diamonds should be produced or sold.
“Standards exist precisely because industries evolve”, Mr. Sheintal continues. “Therefore, the question before us is not whether synthetic diamonds should exist. They are legitimate products, manufactured through impressive technological innovation and serving legitimate consumer demand. Nor is the question whether manufacturers of synthetic diamonds should be entitled to market their products successfully. The question is considerably more fundamental. Do the words we use today continue to fulfil the purpose for which international nomenclature was originally created?”
Implications for Jewellers
If adopted, the proposed changes could affect how natural and synthetic diamonds are described in product information, sales materials and other consumer-facing communications.
CIBJO’s Blue Books provide industry standards and nomenclature for use across the jewellery supply chain, although their application is voluntary.
The issue also has implications for laboratories and diamond grading reports. The report references changes by the Gemological Institute of America towards descriptive terminology for synthetic diamonds rather than applying the traditional grading approach.
Industry Consultation
In preparing the report, Mr. Sheintal invited contributions from Diamond Commission members and other industry officials, including Jean Piere Chalain, Diamond Commission vice president; Thomas Lind, vice president of CIBJO’s Sector A, which covers all gem materials; Peter Karakchiev, head international relations at ALROSA; and Alan Cohen, a member of the Diamond Commission.
The proposed amendments to the Diamond Blue Book will be considered as part of discussions at the 2026 CIBJO Congress in Vicenza.
