Milan: The Diamond Commission of the World Jewellery Confederation (CIBJO) has insisted that the 4C polished diamond grading system (cut, color, clarity, and carat weight) should only be used for natural stones, but not synthetic ones.

In the Special Report prepared for the upcoming 2026 CIBJO Congress, the Commission’s head Udi Sheintal also urged the industry’s stakeholders to use the word “synthetic” as the preferred term to describe diamonds created through industrial processes.

“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,” he noted.

“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.”

According to Sheintal, the 4C classification is a “tool intended to define the rarity and uniqueness of natural stones.” Since synthetic diamonds are inherently man-made products, “they should be subject to a specific quality-control nomenclature.”

The new edition of the CIBJO Congress is set to take place in Vicenza, Italy, on September 4, 2026.