Unfortunately, the evaluation criteria of different institutes are not always the same, which means that the same diamond can be assessed differently by different institutes. For this reason, when comparing the prices of two diamonds with the same rating, it is important to ensure that the certificates of both stones come from the same gemological institute.

The most renowned gemological institute worldwide is the Gemological Institute of America, known as GIA. Since 1931, GIA has been the leading expert organization for gemology globally. Its diamond classification, introduced in 1953, is considered an internationally recognized standard. GIA is the strictest institute in terms of qualification, and many customers only purchase diamonds if they have a GIA certificate. 

The quality of all ONE diamonds is guaranteed by a GIA certificate. The unique certificate number is laser-engraved on the girdle of all ONE diamonds. This engraving is not visible to the naked eye, therefore it does not affect the brilliance or appearance of the diamond in any way, but it can be deciphered under a magnifying loupe. This ensures without a doubt that the diamond and the certificate belong together, preventing any confusion or substitution.