What Does a Lab-Diamond Grading Report Show, and Is a Seller’s Report Enough?

ZKZ Editorial TeamMain answer · Product & gemmology desk

An independent lab report confirms the stone is laboratory-grown and records measurable facts: weight, measurements, quality grades or assessment, and any disclosed treatment, usually with a report number and girdle inscription you can check. A seller’s own certificate is a description, not independent verification. For small accent stones it is usually enough; for stones around half a carat and up, an independent report is worth asking for.

What a report records

Fact Labs differ in format. IGI lab-grown reports grade the 4Cs and usually note the growth method. Since 1 October 2025, GIA classifies colourless and near-colourless lab-grown stones (0.15 ct and up) as “Premium” or “Standard” instead of giving D-to-Z colour grades, and laser-inscribes “Laboratory-Grown” and the assessment number on the girdle. Stones below its Standard criteria receive no GIA assessment.

Fact FTC guidance says treatments that significantly affect value should be disclosed, so look for any treatment notes on the report.

How to check a report

1. Look up the report number on the issuing lab’s website and confirm the details match.
2. Compare carat weight and millimetre measurements with the stone you receive.
3. Find the girdle inscription with a 10x loupe, if one is listed.
4. Confirm the report says laboratory-grown.

When a seller certificate is enough

• Usually enough: pavé, melee and small studs, where individual reports are uncommon and add significant cost per stone.
• Ask for more: centre stones and larger studs, where grade differences affect price and appearance.

What a seller certificate should include

If you do accept a seller’s certificate, check that it is specific. It should name the stones as laboratory-grown, give carat weight and, ideally, millimetre measurements, describe colour and clarity in terms the seller will stand behind, and be tied to the item by a reference number on your invoice. A generic “certificate of authenticity” with no stone details tells you very little. Our own certificate page shows what accompanies our pieces.

Where the limits are

Uncertain Grading standards differ between labs, so the same stone may not receive identical grades everywhere. Compare reports from the same lab where you can. A report also does not state value. Valuations for insurance are a separate document.

Sources

• GIA: Laboratory-grown diamond services
• GIA press release (Aug 2025): updated laboratory-grown diamond services
• IGI: Lab-grown diamond report
• FTC: In the Loupe, advertising diamonds, gemstones and pearls

Fact = stated by the cited source. Our advice = editorial recommendation. Uncertain / it depends = limits of what can be said in general.