A diamond certificate, more accurately called a grading report, is an independent laboratory’s assessment of a diamond’s characteristics. It does not set a price, but it gives you an objective description of exactly what you are buying, so you can compare diamonds fairly.
What every good report includes
- A unique report number, ideally laser-inscribed on the diamond’s girdle.
- Whether the diamond is natural or laboratory-grown, and any treatments.
- Shape, measurements and carat weight.
- Colour and clarity grades, and a cut grade for round brilliants.
- Polish, symmetry and fluorescence.
- An online verification service so you can check the report yourself.
GIA – Gemological Institute of America
Founded in 1931, GIA is a non-profit institute that created the 4Cs grading system and the D-to-Z colour scale used around the world. GIA reports are widely regarded as the benchmark for natural diamonds, and GIA also grades laboratory-grown diamonds.
IGI – International Gemological Institute
Founded in Antwerp in 1975, IGI has laboratories in many countries and grades both natural and laboratory-grown diamonds. It certifies a large share of the world’s lab-grown diamonds. Read our full guide on how to read an IGI report.
WGI – World Gemological Institute
WGI is an independent gemmological laboratory that issues grading reports for natural and laboratory-grown diamonds and coloured gemstones. A WGI report covers the same core characteristics – shape, measurements, carat weight, colour, clarity and, where relevant, cut – and carries a report number that can be checked with the laboratory. As with any report, it is a description of that particular stone, and grading standards can differ slightly between laboratories, so it is best to compare diamonds graded by the same laboratory.
Which report should you look for?
- Natural diamonds: a GIA or IGI report gives the most widely recognised description.
- Laboratory-grown diamonds: IGI and GIA reports are the most common; check that the report clearly states “laboratory-grown”.
- Smaller diamonds (for example halo or pavé stones) are not usually graded individually; their total weight and typical quality are described by the jeweller instead.
Always verify
Whichever laboratory graded your diamond, enter the report number on the laboratory’s own website and check that the measurements and weight match. A jeweller can confirm the girdle inscription under magnification.
Our approach
Each product page tells you which certification is available for that design, and our diamonds are described honestly as natural or lab-grown. If you would like to see a diamond and its report before you buy, book an appointment at our Hatton Garden showroom or read more in our diamond guide.
