IGI or GIA? Diamond grading reports explained
Updated 16 October 2026
A grading report, often called a certificate, is an independent laboratory's assessment of a diamond. It records the shape, measurements, carat weight, colour, clarity and, for round brilliants, cut grade. It also states whether the diamond is laboratory-grown or natural.
Who issues them
The two names you will see most are the Gemological Institute of America (GIA) and the International Gemological Institute (IGI). Both are long-established and widely recognised.
- IGI grades a large share of the world's laboratory-grown diamonds, and also grades earth-mined stones. Its reports give full colour, clarity and cut grades for both.
- GIA is the reference laboratory for earth-mined diamonds. In 2025 it announced that its reports for laboratory-grown diamonds would move away from the full 4Cs grading scale to simpler descriptive terms.
Because of that change, we use IGI reports for laboratory-grown diamonds, so you get full grades, and IGI or GIA reports for earth-mined diamonds.
How to check a report
- Find the report number on the paperwork.
- Enter it on the issuing laboratory's own website. You should see the same details.
- Many diamonds carry the report number laser-inscribed on the girdle. Ask us to show it to you under magnification.
Every Audley diamond over 0.30 ct comes with its report, and we send you the number before you pay so you can check it yourself.