Independent proof
The grades come from a laboratory, not the seller, so you can compare diamonds fairly.
Certification
Diamond Certification Explained
A diamond certificate is your independent proof of exactly what you’re buying. Here’s what a grading report includes, how GIA and IGI compare, and how to check a report yourself.
What it is
A grading report, from an independent laboratory
A diamond “certificate” is properly called a grading report. It’s issued by an independent gemmological laboratory that examines the diamond and records its characteristics — the 4Cs, measurements, proportions and more — without any interest in the sale.
It’s not a valuation. A grading report describes quality; it doesn’t put a price on the diamond. For insurance you’ll need a separate valuation.
Why it matters
Why you should never buy without one
Fair comparison
Two diamonds that look alike can be graded very differently. A report shows exactly what separates them.
Natural or lab-grown
The report confirms the diamond’s origin and records any treatments.
Insurance and resale
Insurers and future valuers rely on the report to identify and describe your diamond.
The laboratories
GIA and IGI compared
Primo diamonds are graded by GIA or IGI, two of the world’s most widely recognised laboratories.
| GIA | IGI | |
|---|---|---|
| Full name | Gemological Institute of America | International Gemological Institute |
| Founded | 1931, USA | 1975, Antwerp |
| Known for | Creating the 4Cs and the international diamond grading system; the benchmark for natural diamonds | A global network of labs; the most widely used laboratory for lab-grown diamonds |
| Grades natural diamonds | Yes | Yes |
| Grades lab-grown diamonds | Yes | Yes |
| Check a report online | GIA Report Check | IGI Verify Your Report |
Grading standards differ slightly between laboratories, so it’s best to compare diamonds graded by the same lab.
Reading a report
What’s on a grading report
- Report number and dateunique to your diamond; often laser-inscribed on the diamond’s girdle
- Shape and cutting stylefor example, round brilliant or emerald step cut
- Measurementslength, width and depth in millimetres
- Carat weightto two decimal places
- Colour gradeon the D–Z scale
- Clarity gradefrom Flawless to Included
- Cut gradefor round diamonds
- Polish and symmetryhow precisely the facets are finished
- Fluorescencehow strongly the diamond glows under UV light
- Proportions diagramtable size, depth and angles
- Clarity plota map of the diamond’s inclusions (on full reports)
- Commentsorigin, treatments or other notes
Lab-grown diamonds
How lab-grown diamonds are reported
A lab-grown diamond’s report clearly states that it was laboratory grown, and the diamond itself is usually laser-inscribed to say so. Reports may also record the growth method (such as CVD or HPHT) and any treatment after growth.
[CLIENT TO CONFIRM: which lab grades your lab-grown diamonds, and what format the report uses — report formats for lab-grown diamonds have changed recently at some labs.]
Verify
How to check a certificate yourself
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Find the report number
It’s printed on the report and on any digital copy.
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Look for the inscription
Many diamonds have the report number laser-inscribed on the girdle, visible under a jeweller’s loupe. We’re happy to show you.
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Check online
Enter the number on the laboratory’s website (GIA Report Check or IGI Verify Your Report) to see the official record.
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Match the details
Make sure the shape, measurements, carat and grades match the diamond you’re buying.
Don’t confuse them
Grading report vs valuation
| Grading report | Valuation | |
|---|---|---|
| Issued by | An independent laboratory | A qualified valuer or jeweller |
| Describes | Quality: the 4Cs and measurements | Replacement value in money |
| Used for | Comparing and identifying diamonds | Insurance |
| Changes over time? | No — the diamond’s grades don’t change | Yes — should be updated every few years |
Buying from Primo
Every centre diamond, independently graded
Every Primo centre diamond comes with an independent grading report from GIA or IGI, and we’ll walk you through it before you decide — what each grade means, and how it shows in the diamond in front of you.
[CLIENT TO CONFIRM: is there a minimum size for certified centre stones? Do you provide a valuation for insurance? For natural diamonds, confirm wording on responsible sourcing, e.g. Kimberley Process / System of Warranties.]
Questions
Frequently asked questions
Is a diamond certificate the same as a valuation?
No. A certificate (grading report) describes the diamond’s quality; a valuation puts a monetary value on it, usually for insurance.
Is GIA better than IGI?
Both are respected, independent laboratories. GIA is the long-established benchmark for natural diamonds; IGI is the most widely used for lab-grown diamonds. Compare diamonds graded by the same lab where you can.
Can I check a certificate is genuine?
Yes. Enter the report number on the laboratory’s website and check that the details match. Many diamonds are also laser-inscribed with the report number.
Do small diamonds come with certificates?
Centre stones usually do. The small diamonds in halos and pavé bands are normally not individually graded.
What does the laser inscription mean?
It’s a tiny engraving of the report number on the diamond’s edge, invisible to the naked eye, that links the diamond to its report.
Does a certificate prove a diamond is natural?
Yes — the report states whether the diamond is natural or laboratory grown.
Continue reading
Related guides
See a report alongside the diamond
Visit our Hatton Garden showroom and we’ll show you how a grading report matches the diamond in front of you — including the inscription under the loupe — with no pressure to decide on the day.