A diamond grading report is an independent description of a diamond’s quality, written by a gemmological laboratory that has no interest in selling the stone. The International Gemological Institute (IGI), founded in Antwerp in 1975, is one of the largest of these laboratories and grades both natural and laboratory-grown diamonds. Many of our lab-grown diamonds are supplied with an IGI report.
What an IGI report shows
- Report number – a unique number you can look up on the IGI website.
- Shape and cutting style – for example round brilliant, oval or emerald cut.
- Measurements – length, width and depth in millimetres.
- Carat weight – weighed to the hundredth of a carat.
- Colour grade – on the D (colourless) to Z scale.
- Clarity grade – from flawless (FL) through VVS, VS and SI to included (I).
- Cut grade (round brilliants), plus polish and symmetry.
- Fluorescence – how the diamond reacts to ultraviolet light.
- Plotted diagram – a map of the main inclusions, and often a laser inscription of the report number on the girdle.
IGI reports for lab-grown diamonds
An IGI report for a laboratory-grown diamond clearly states that the stone is laboratory-grown. It may also note the growth method, such as CVD (chemical vapour deposition) or HPHT (high pressure, high temperature), and whether the diamond has had any post-growth treatment to improve its colour. The laser inscription on the girdle normally includes the words “LG” or “Laboratory Grown” with the report number.
How to check a report
Enter the report number on the IGI website’s report verification page and compare the details with your paper or digital report. The measurements and carat weight should match the diamond exactly, and a jeweller can read the girdle inscription under magnification to confirm it is the same stone.
IGI or GIA?
Both are respected independent laboratories. GIA is particularly well known for natural diamonds, while IGI grades a very large share of the world’s laboratory-grown diamonds. Read our guide to diamond certificates from GIA, IGI and WGI for a side-by-side comparison.
Shop certified diamonds
The product page for each piece shows which certification is available for that design. Explore lab-grown diamond engagement rings and natural diamond engagement rings, or book an appointment to see a certified diamond and its report in person.