Verify the certificate
Updated November 2026
A diamond's grades set its price, and the grades are only real if an independent lab stands behind them. This check takes 30 seconds, costs nothing, and is skipped by almost every first-time buyer — which is exactly why the shady corners of the industry still work.
The check: the stone has a GIA or IGI report, the report number looks up on the lab's own website and matches the stone's specs, and the girdle inscription matches the number. Anything less is a hard no.
Run it
- Ask for the report number. Any legitimate seller hands it over instantly — it's printed on the report and usually in the listing. Hesitation is data.
- Look it up on the lab's site. GIA Report Check (gia.edu) or IGI Verify (igi.org). Free, instant, no account.
- Match the specs. Carat, color, clarity, cut, measurements — the lookup should match the stone you're being quoted, line for line.
- Check the inscription. Most certified stones have the report number laser-inscribed on the girdle. Ask to see it under the jeweler's loupe — good sellers offer before you ask.
- Confirm origin wording. The report states "natural" or "laboratory-grown" plainly. The price should match the word. (That gap is the whole subject of check 4.)
Which paper counts
| Paperwork | Verdict | Why |
|---|---|---|
| GIA report | Pass | The strictest grader in the business; the standard for natural stones. |
| IGI report | Pass | Grades most of the world's lab-grown diamonds; trusted and verifiable. |
| GCAL report | Pass | Smaller lab, solid guarantee model. Less common, still independent. |
| Store "certificate of authenticity" | Fail | The seller grading their own inventory. That's a menu, not an inspection. |
| Appraisal showing a big "retail value" | Fail | Insurance paperwork dressed up as a discount. See the red flags sweep. |
| No paperwork, "trust me" pricing | Fail | You can't comp it, insure it properly, or resell it credibly. Walk. |
One nuance worth knowing
GIA grades conservatively, so the market pays a little more for a GIA-graded stone than an identically graded stone from a softer lab — the grades are simply trusted more. Practical rule: on natural stones, prefer GIA and compare stones within the same lab's grading. On lab-grown, IGI is the market norm and perfectly fine; spend your attention on cut quality instead (that's check 2).