Diamond grading reports
A grading report describes a diamond. It doesn’t show you how it looks.
From the CTJ Jewellery team, led by founder Greg Ward
A grading report, commonly called a diamond certificate, is issued by an independent laboratory. It records the diamond’s measurements and grades and states whether it is natural or lab-grown. Natural and lab-grown diamonds are supplied with grading reports from internationally recognised laboratories where applicable.
GIA and IGI
GIA
Gemological Institute of AmericaAn independent laboratory that issues internationally recognised diamond grading reports. Founded in 1931, it developed the four Cs grading system.
IGI
International Gemological InstituteAn independent laboratory that grades natural and lab-grown diamonds. Founded in Antwerp in 1975.
What a report records
- Shape and measurements
- To 0.01 mm
- Carat weight
- To 0.01ct
- Colour grade
- D to Z
- Clarity grade
- With a plotted diagram of inclusions
- Cut, polish, symmetry
- Excellent to poor
- Fluorescence
- None to very strong
- Origin
- Natural or laboratory-grown
- Report number
- Laser-inscribed on the girdle of graded diamonds
Check the report number against the inscription on the girdle. We’re happy to show you both under the loupe.
Why the report isn’t the whole story
A report records grades, not beauty. Two diamonds with identical reports can look very different in real life. That’s why we select diamonds for visual performance and encourage you to compare them side by side.