Diamond certificate buying guide

What is diamond certification?

Certification refers to the process of having a diamond graded and evaluated by an independent gemological laboratory. The most well-known certification agency globally is the Gemological Institute of America, or GIA - they are known to have the tightest and highest grading standards. Meaning if the diamond is graded in two separate GIA labs by different GIA gemologists, the grading should be the same. In terms of their high grading standards, a GIA F colour diamond for example may be graded as an E colour by another lab with lower standards - or another labs F colour may only be graded as a G colour by the GIA. Other popular labs are AGS, HRD and IGI. The certification report includes information on the diamond's cut, clarity, colour, carat weight, and other characteristics.

Certification provides assurance to buyers that they are getting a genuine and accurately graded diamond. The main way to check if your diamond matches the certificate is to have a jeweller read the inscription on the diamond’s girdle, this should match the report number. The vast majority of diamonds you’ll find available today will have a laser inscription.

As of 2023, a lot of natural and lab grown diamonds only have an online certificate, not an original physical copy.

Example of a GIA certificate

Which diamond certification should I buy?

With GIA being the most recognized globally, and having high grading standards, it's my go to certificate. Other certificates you can buy include AGS (popular in the US), HRD and IGI. Typically you will pay a slight premium for a GIA certificate, so if you are looking to save some cash then consider all of these and just ensure you are happy with the look of the diamond.

Lab grown diamond certificates

With lab grown diamonds, I typically advise buying a high spec diamond, and as you shouldn’t take reselling into account, I typically suggest IGI certified diamonds for my customers. IGI is the most popular choice of certificate for lab grown diamond cutters as they have been grading lab grown diamonds for longer than the GIA. If a diamond was graded by the GIA, yes it may have a slightly lower grade, but if you buy a high spec such as E colour VS1 clarity and Ideal cut, you can be sure it will look amazing anyway! You can buy GIA certified lab grown diamonds, but they do not come with a hard copy certificate, you will pay a premium on them and if you buy a high spec diamond there would be no visual difference anyway.