When a diamond is described as "certified", it usually means that an independent gemmological laboratory has examined it and issued a document describing its characteristics. Laboratories generally call this document a grading report rather than a certificate, because it describes the stone rather than guaranteeing anything about it.
What a grading report contains
- A report number, which may also be laser-inscribed on the diamond's girdle.
- Shape, cutting style and measurements.
- Carat weight, colour grade and clarity grade.
- For round brilliants, a cut grade; for all shapes, polish and symmetry.
- Fluorescence.
- Whether the diamond is natural or laboratory-grown, and any treatment detected.
- Often a diagram of the inclusions and a proportions diagram.
What a report is not
- Not a valuation. It does not state a price or an insurance value; that is the role of an appraisal.
- Not a guarantee of ethics or sustainability. A standard grading report describes the stone, not its supply chain.
- Not identical everywhere. Different laboratories may apply grading standards differently. Read GIA vs IGI.
Checking that the report matches the stone
- Verify the report number on the laboratory's website.
- Compare the measurements and weight with the stone you are shown.
- If there is a girdle inscription, ask to see it under magnification.
A word on the Kimberley Process
The Kimberley Process Certification Scheme, in force since 2003, governs the international trade in rough diamonds and aims to prevent conflict diamonds from entering the market. It concerns shipments of rough stones; it is not a grading report and does not describe an individual polished diamond.
How DORVETTI uses the word
We describe a stone as accompanied by a report only when that report exists, name the laboratory that issued it, and make its details available. We never use "certified" as a general quality claim. This article is general information and does not constitute legal advice.
Types of documents
| Document | What it is |
|---|---|
| Full grading report | The complete description of a diamond, often with a plot of its inclusions |
| Shorter reports | A condensed format, usually without the inclusion plot, common for smaller stones |
| Identification report | Confirms what a stone is, and any treatments detected, without grading its quality |
| Origin report | For some coloured gems, an opinion on geographic origin |
| Appraisal or valuation | An estimate of value, usually for insurance; not a grading document |
Red flags
- A "certificate" issued by the seller itself rather than an independent laboratory.
- A report number that cannot be verified, or measurements that do not match the stone.
- An appraisal value far above the price, used as a selling argument.
- Vague wording about origin or treatment.
Keeping your documentation
Keep the report, the invoice and a photograph of the piece together, and a copy somewhere separate. They help with insurance, repairs and, one day, with passing the piece on.
Sources: Gemological Institute of America (gia.edu), the 4Cs of diamond quality and GIA grading scales; International Gemological Institute (igi.org), laboratory information; Kimberley Process Certification Scheme (kimberleyprocess.com).
Frequently asked questions
Is a certified diamond better?
A report does not make a diamond better; it describes it. Its value is that an independent laboratory has examined the stone.
Is a grading report a valuation?
No. A report describes quality; it does not state a price or an insurance value.
How can I check a report?
Most major laboratories let you verify a report number online, and many diamonds carry the number laser-inscribed on the girdle.
Do small diamonds come with reports?
Often not. Grading every small stone would add disproportionate cost; small stones are usually described by their total weight and an approximate quality range.
Does a report prove a diamond is conflict-free?
A standard grading report describes the stone, not its supply chain. Ask the seller separately about sourcing and the documentation they hold.
