IGI vs GIA: How to Compare Diamond Reports

“Diamond certificate” is a common retail term for a laboratory report. Read the document’s title to establish whether it provides grading, identification, an overall quality assessment or another service.

A grading report and an appraisal serve different purposes. The report documents assessed characteristics; an appraisal estimates monetary value. A report therefore does not establish the price you should pay or the amount a future buyer might offer. GIA’s explanation of grading reports and appraisals.

Request the complete document when comparing offers. A listing that says only “IGI certified” or “GIA certified” leaves the report type and recorded results unexplained.

For the broader introduction, visit our diamond certificates guide.

The comparison should continue beyond this overview. Read the complete document and the relevant service description before treating two listings as equivalent.

For natural diamonds, IGI records details including shape, cutting style, measurements and quality grades. Depending on the report, additional information may include a proportions graphic, clarity diagram and comments about an inscription. IGI’s natural diamond report guidance.

GIA also offers several natural-diamond report formats. Its Diamond Grading Report includes a plotted clarity diagram, while the Diamond Dossier does not. The Dossier includes a report-number inscription as part of its service. GIA’s report comparison.

This means that two documents can differ because different services were selected, even when the same laboratory issued them.

Before comparing individual grades, establish whether both documents cover the information you need. If a clarity plot matters to your assessment, request a report format that includes one. If the document contains comments or limitations, read them alongside the headline grades.

For laboratory-grown diamonds, an IGI report can provide individual colour and clarity grades alongside measurements and other assessed characteristics. Growth method and post-growth treatment information may also be reported, depending on the service. IGI’s laboratory-grown report guidance.

GIA’s current service for eligible colourless to near-colourless laboratory-grown diamonds gives an overall Premium or Standard assessment. Its laboratory-grown coloured diamond services use separate formats, so the same description should not be applied to every GIA laboratory-grown document. GIA’s current laboratory-grown services.

Premium and Standard combine several criteria. For example, GIA’s published Premium requirements include D colour and VVS clarity or higher, together with specified finish and applicable cut requirements. Premium therefore does not identify one exact clarity grade. GIA’s published assessment criteria.

When comparing an IGI document showing an individual clarity grade with a GIA overall assessment, preserve that distinction. Ask which characteristics each document establishes and which additional details come from the seller.

Our IGI laboratory-grown diamond report guide and GIA laboratory-grown diamond report guide explain the respective documents in more detail.

GIA announced that its revised laboratory-grown diamond assessment service would begin on 1 October 2025. Earlier documents can therefore use terminology associated with the previous service. GIA’s service-change announcement.

The practical implication is to check the document’s date and format together. A difference from today’s sample does not, by itself, establish that an earlier document is false.

Verify the recorded information with GIA and ask the issuer about any uncertainty concerning an older document. Keep the original assessment distinct from a seller’s later description of the stone.

If a purchase specifically requires current documentation, establish that requirement before agreeing to the transaction. Ask which service would be needed and what information it would provide.

The item examined also affects the document’s scope.

IGI offers finished-jewellery reports that identify mounted gemstones and describe relevant metal information. For mounted diamonds, measurements and grading are assessed as the mounting permits. IGI’s explanation of finished-jewellery reporting.

When reviewing a ring, establish whether the accompanying document covers the loose centre diamond or the completed jewellery piece. A centre-stone report should not be treated as documentation for every side stone or the metalwork.

Ask the seller to connect each document to the item it describes. This is particularly useful when a quotation includes several diamonds, a separate centre-stone report and a jewellery appraisal.

Start with the issuing laboratory’s own verification service. Enter the report number through IGI’s report verification or GIA Report Check, then compare the available record with the document supplied.

Review the identifying information, measurements and recorded results. Resolve any discrepancy with the seller and, where necessary, the laboratory.

The next step is connecting that record to the physical stone. A working report number alone cannot establish that connection. GIA has documented a moissanite carrying a copied inscription whose number belonged to a natural diamond; the stones had different measurements. GIA’s investigation of a fraudulent inscription.

Ask a qualified gemmologist or jeweller to compare the diamond with its documentation, including the inscription where present and other identifying characteristics. If an inscription is difficult to inspect in a setting, discuss an appropriate verification method.

Start with the information your purchase requires.

For a natural diamond, compare the exact report formats and the characteristics recorded. For a laboratory-grown diamond, establish whether you need individual grades, an overall assessment or particular production information.

A jeweller purchasing for a client should agree any laboratory or report requirements before sourcing. A consumer can ask the seller to explain how the available document supports the advertised description.

If someone recommends one laboratory as universally “stricter”, ask what evidence supports that statement for the service being discussed. Keep any such claim separate from the actual results recorded for the diamond.

If you are commissioning a new assessment, confirm the relevant service, submission requirements, current fee and expected return time with the laboratory. Broad claims about which organisation is always faster or cheaper are insufficient for planning a particular submission.

The document is one part of the purchase decision. Review the actual stone’s appearance, the complete quotation and the seller’s purchase terms alongside it.

To discuss a diamond purchase, contact Uniglo Diamonds with your preferred diamond origin, shape, size and any laboratory-document requirements.

Ask to review the documentation for the individual stone, together with its specifications and current quotation. Where report formats differ, request a clear explanation of what each document establishes.