First defined diamond grading system ratified

Princess cut diamond. (Reference image by Mark Johnson | Serendipity Diamonds, Flickr).

CIBJO, the World Jewellery Confederation, has described as ‘ground-breaking’ the publication by the International Standards Organisation of ISO 24016, the first-ever standard approved by the body that specifies the terminology, classification and methods to be used for the grading and description of single unmounted polished diamonds of more than 0.25 carats.

“It is the first time than a strictly defined diamond grading system has been ratified by the world’s leading standards body, formally recognizing principles and terminology that to date have not been approved by any impartial and international authority,” the Confederation’s president, Gaetano Cavalieri, said in the brief.

“ISO 24016 essentially parallels the CIBJO Diamond Blue Book, meaning that our widely-accepted standard is now effectively validated by ISO.” 

ISO 24016 applies to natural, unmounted, polished diamonds not to fancy coloured or synthetic diamonds

According to the introduction in ISO 24016, the aim of a standard for grading unmounted polished diamonds is to set rules for determining with maximum precision and accuracy the mass, colour, clarity and cut of individual polished diamonds.

“On one hand, based on these four criteria –  also known as ‘the 4Cs’ – the diamond trade evaluates the value of diamonds. On the other hand, some diamond grading reports may be issued based on different standards by different laboratories, potentially leading to different results for the same individual diamond. This situation damages the reputation of the whole diamond trade. Hence, the need for a unique ISO standard for grading polished diamonds,” the document reads.

ISO 24016 applies to natural, unmounted, polished diamonds not to fancy coloured diamonds, synthetic gems, diamonds treated by methods other than laser drilling, nor to assembled stones.

The process of developing a new standard for diamond grading began two years ago at the request of Schweizerische Normen-Vereinigung, the Swiss Association for Standardisation. 

Back then, CIBJO granted ISO permission to use its own Publicly Available Specification PAS 1048, based on the CIBJO Diamond Blue Book, as a basis for drafting the new guidelines.