The Gemological Institute of America (GIA) has announced the details of its new grading criteria for lab-grown diamonds.💎

The GIA has introduced new guidelines for grading lab-grown diamonds, effective October 1, 2025, by separating their quality assessment from natural diamonds and moving away from the traditional 4Cs. Submitted lab-grown diamonds will now be categorized as either "Premium" or "Standard," with specific clarity, color, and finish criteria for each. Stones not meeting the minimum "Standard" criteria will receive no GIA assessment.

The institute which will start issuing certificates with the updated format on October 1 will use the terms “Premium” and “Standard” to describe synthetics, rather than the usual GIA nomenclature, it said Wednesday. The clarity, color and cut will determine which of those new ratings the stone receives in its GIA Laboratory-Grown Diamond Quality Assessment, which the institute first revealed in June. “Using descriptive terms for the quality of laboratory-grown diamonds is appropriate, as most fall into a very narrow range of color and clarity,” explained GIA CEO Pritesh Patel on Wednesday. “Because of that, the GIA will no longer use the nomenclature created for natural diamonds to describe what is a manufactured product.” To earn the Premium label, lab-grown diamonds must be D-color and have a minimum clarity of VVS, as well as excellent polish and symmetry; round brilliant stones will also require an excellent cut grade. The Standard category is for stones with a color range of E to J and VS clarity. They must also have a polish rating of “very good,” plus a symmetry of “good” for fancy shapes and “very good” for round brilliants which should bear the same rating for cut grade. Synthetics that have a combination of Premium and Standard criteria will be graded as Standard, the GIA clarified. The GIA will charge $15 per carat for each report, with a minimum fee of $15 meaning a certificate for a 5-carat diamond would cost $75, while one for a 0.50-carat stone would be $15. The institute will only accept synthetics of 0.15 carats and above. Each stone that meets the lab’s criteria for a report will have its girdle laser-inscribed with the term “laboratory-grown” and a GIA quality-assessment number. The institute will then return the diamond with a printed document containing the results. Stones that don’t meet the criteria for a Standard grade will not receive a report, according to the GIA; the lab will send them back, and the submitter will still need to pay a $5 evaluation fee. The current GIA reports for D to Z lab-grown diamonds will be available until September 30.