GREMARI GUIDE
IGI and GIA diamond reports: what certification really tells you
When you buy a diamond, an independent gemological report gives you objective information about the stone. It can confirm origin, document quality characteristics and provide a report number that can be checked against the laboratory’s records.
“Certificate” or “grading report”?
In everyday jewellery language, people often say “diamond certificate”. Gemological laboratories generally use terms such as grading report, quality assessment or identification report.
The distinction matters because a grading report is not a valuation and it does not guarantee a future resale price. It is an independent description of the diamond at the time it was examined.
What is IGI?
IGI — the International Gemological Institute — issues reports for natural diamonds, laboratory-grown diamonds, gemstones and finished jewellery.
For laboratory-grown diamonds, IGI identifies the stone as laboratory-grown and documents relevant characteristics including the 4Cs. IGI states that it screens gemstones to determine whether they are naturally mined, laboratory-grown or simulants, and may include information on growth process or treatments in report comments where applicable.
IGI also uses laser inscription services. A report number can be inscribed on the girdle of a diamond, creating a direct link between the physical stone and its report.
What is GIA?
GIA — the Gemological Institute of America — developed the modern 4Cs terminology and the International Diamond Grading System used throughout the diamond industry.
For natural diamonds, GIA reports continue to use the familiar grading scales for colour, clarity, cut and carat weight.
An important change for GIA lab-grown diamonds
GIA changed its reporting system for colourless-to-near-colourless laboratory-grown diamonds on 1 October 2025.
Instead of using the same detailed colour and clarity nomenclature used for natural diamonds, qualifying laboratory-grown stones now receive an overall quality classification of:
- Premium, or
- Standard.
The assessment is based on a combination of colour, clarity, polish, symmetry and cut criteria. A stone that does not meet the minimum criteria for Standard does not receive that GIA laboratory-grown quality designation.
So is IGI better than GIA?
That is not a useful way to frame the question. Both are established gemological laboratories, but their current reporting formats for laboratory-grown diamonds are different.
- IGI generally provides detailed 4Cs-style grading information.
- GIA uses its newer Premium/Standard overall quality assessment for qualifying colourless-to-near-colourless lab-grown diamonds.
What about HRD Antwerp?
HRD Antwerp is another recognised gemological laboratory. It issues separate reports for natural and laboratory-grown diamonds and clearly identifies laboratory-grown origin. HRD states that its laboratory-grown reports use the same 4Cs nomenclature as its natural diamond reports while making the origin explicit.
What should you actually look for on a report?
- Origin: the report should clearly state whether the diamond is natural or laboratory-grown.
- Report number: use the laboratory’s official report-check service where available.
- Carat weight: the precise weight of the diamond.
- Measurements: useful for understanding visible size and proportions.
- Quality information: colour, clarity, cut or the laboratory’s current equivalent assessment.
- Polish and symmetry: indicators of finishing quality.
- Laser inscription: where present, it can help match the diamond to the report.
- Comments: may contain information about treatments, growth method or other relevant observations.
Can a grading report tell you whether a diamond is beautiful?
Not completely. A report is an essential technical document, but it is not a photograph and it cannot replace visual judgement. Two diamonds with similar grades can still look different because of proportions, facet pattern, inclusion placement and the way each stone interacts with light.
Can a report tell you what the diamond is worth?
No. A grading report is not an appraisal. It documents the diamond’s characteristics; it does not set a retail price or guarantee future value.
A good diamond report should make your purchase more transparent, not more complicated.
