The International Standards Organization (ISO) has approved its first grading guidelines for polished diamonds in an effort to achieve consistency among laboratories.
The new ISO 24106 specifies the terminology, classification and methods that labs should use when grading and describing loose stones, the World Jewellery Confederation (CIBJO) said Wednesday. Implementing the instructions is voluntary, unless an individual country rules otherwise.
“Some diamond-grading reports may be issued based on different standards by different laboratories, potentially leading to different results for the same individual diamond,” the ISO says in its introduction to the book, which it published this month. “This situation damages the reputation of the whole diamond trade. Hence the need for a unique ISO standard for grading polished diamonds.”
The 55-page standard, which uses the CIBJO Diamond Blue Book as its basis, applies to natural, unmounted, polished diamonds weighing more than 0.25 carats. It does not apply to fancy-color diamonds, lab-grown diamonds, or goods treated via methods other than laser-drilling.
The Swiss Association for Standardization requested the new standard two years ago, CIBJO said. CIBJO subsequently granted the ISO permission to use its existing standard for the new guide.
Its publication follows the ISO’s guide to general terminology for natural and synthetic diamonds and simulants, which it released in 2015 and reconfirmed last week following a five-year review. The guide is notable for defining diamonds as a natural mineral, in contrast to the US Federal Trade Commission’s wording, which dropped the word “natural” in 2018.
“There is no doubt in my mind that these two international ISO standards, together with the CIBJO Diamond Blue Book, will help boost consumer confidence,” said Udi Sheintal, president of CIBJO’s Diamond Commission. “The timing is particularly relevant, especially now when clear distinctions must be made between laboratory-grown diamonds and natural diamonds.”