What is a diamond certificate?
A diamond certificate (also called a grading report) is an independent assessment of a diamond's characteristics by a gemological laboratory. The lab evaluates the 4Cs along with measurements, proportions, fluorescence, and additional details — and issues a written report.
A certificate is your guarantee. It is the only objective record of what the diamond actually is. Never buy a fine diamond without one.
The major laboratories
GIA (Gemological Institute of America) — Founded in 1931, GIA is the gold standard for natural diamond grading. Universally accepted, consistent, and conservative in its grading. Most natural diamonds above 0.5ct should have a GIA certificate.
IGI (International Gemological Institute) — Founded in 1975, IGI is the leading authority for lab-grown diamonds. IGI's lab-grown grading is highly trusted; their natural grading tends to be slightly more lenient than GIA.
AGS (American Gem Society) — Founded in 1934, AGS is known for its proprietary 0–10 cut grading scale, considered by some to be even more rigorous than GIA's. As of 2023, AGS reports are issued through GIA.
Certificates we accept
We exclusively sell diamonds graded by GIA, IGI, or AGS. We do not accept certificates from less rigorous laboratories such as EGL or HRD, where grading standards have historically been inconsistent.
What's on a certificate
A typical GIA report includes:
- Unique report number (laser-inscribed on the diamond's girdle for verification)
- Shape and cutting style
- Carat weight
- Cut grade (round only)
- Colour grade
- Clarity grade
- Polish and symmetry grades
- Fluorescence
- Measurements (length, width, depth in mm)
- Proportions (table %, depth %, crown angle, pavilion angle, girdle thickness, culet)
- Plotted diagram showing inclusion positions
Verifying a certificate
Every GIA, IGI, and AGS certificate has a unique number that you can verify on the issuing laboratory's website. If a seller cannot provide the certificate or the number doesn't match the lab's records — walk away.