Grading
report
An independent lab document that records a diamond's cut, colour, clarity, carat weight, and proportions under a unique, verifiable report number. The only reliable way to know what you're buying.
A grading report separates the description of a diamond from the seller's interest in the sale. The issuing laboratory has no financial stake in your transaction — its job is to describe the stone accurately and consistently against a defined set of standards.
The report does not tell you what a diamond is worth. It tells you what it is. Value depends on market conditions, demand, setting, and the buyer's preference. Two diamonds with identical grades can sell for different prices depending on cut quality subtleties, fluorescence, and provenance.
Without a report from a recognised lab, every grade claim is the seller's opinion. GIA, IGI, and AGS are the three labs whose reports the mainstream market accepts without question. Others exist, but their grading consistency varies — and some regional labs have documented histories of grade inflation.
- MAIN LABS
- GIA · IGI · AGS
- INCLUDES PRICE
- Never
- VERIFIABLE
- Online + loupe
Lab identity & report type
Identifies the issuing laboratory (GIA, IGI, AGS, etc.), the report type (Diamond Grading Report, eReport, etc.), and the date of issue. The lab name and logo are printed with security features to prevent counterfeiting.
Report number
A unique identifier registered in the lab's database. For GIA reports, this number is also laser-inscribed on the diamond's girdle at microscopic scale — invisible to the naked eye but readable under a loupe. Always verify the report number matches the inscription on the stone.
The four Cs
The core of the report. Carat weight is measured to the nearest 0.01 ct (sometimes 0.001 ct). Colour and clarity are graded under controlled conditions by trained specialists. Cut grade (round brilliants only at GIA) evaluates proportions, symmetry, and polish.
Proportions diagram
A cross-section diagram showing measured proportions: table %, crown angle, crown height %, pavilion angle, pavilion depth %, culet size, and girdle thickness. For round brilliants, these measurements feed into the cut grade model. For fancy shapes, they are the only cut data available.
Clarity plot (full reports)
A diagram showing the type and position of every inclusion and blemish used to determine the clarity grade. Inclusions are marked in red; blemishes in green. Not all report formats include a full plot — eReports and digital reports often omit it. The plot is useful for identifying your specific stone.
Fluorescence & additional info
Records fluorescence strength (None / Faint / Medium / Strong / Very Strong) and colour (usually Blue). Additional information may include treatment disclosures, symmetry grade, polish grade, and comments. Any treatments must be disclosed by the lab.
Reports by lab
Each major lab issues several report formats at different price points and detail levels. All provide the core 4C grades.
- Diamond Grading Report
- Diamond eReport
- Diamond Dossier
- Colored Diamond Report
- Diamond Origin Report
Industry gold standard. Full cut grade for round brilliants. Clarity plot on full reports. Laser inscription standard.
- Diamond Report
- Laboratory Grown Diamond Report
- Colored Diamond Report
- Jewelry Report
Preferred for lab-grown diamonds. Slightly looser grading than GIA. Faster turnaround. Lower cost.
- Diamond Quality Document
- Platinum DQD
- Digital DQD
Numeric cut grade system (0–10). Very strict Ideal grade. AGS Ideal = GIA Excellent or better. Strong US market presence.
- Diamond Grading Report
- Brilliant Report
- Shape Report
Antwerp-based lab. Strong in European trade. Same D–Z / FL–I3 scales. Less common in US/Asian markets.
How to verify a report
Five steps to confirm a grading report is genuine and matches the stone. Do this before any purchase.
Match report number to stone
Use a 10× loupe to find the laser-inscribed report number on the girdle. Verify it matches the certificate. On GIA stones this is standard; always check.
Verify at the lab's website
Every major lab has a public report-check tool. Enter the report number. The database should return the same grades as your physical certificate. If it doesn't match — walk away.
Check the date
A report more than 5–10 years old may not reflect current grading standards (labs occasionally recalibrate). For high-value stones, consider a re-grade if the report is very old.
Inspect security features
Genuine GIA reports have a hologram, microprint line, and security screen. Feel the paper — it is different from standard printer paper. Fakes exist; handle physical certificates with suspicion if something seems off.
Read the comments section
Additional comments on a GIA report can include treatment disclosures, naturals (unpolished girdle areas), extra facets, or graining. These are important disclosures that affect value and are easy to miss.
Report vs appraisal
Two different documents that are often confused — they serve completely different purposes.
What the diamond is
- Issued by an independent gemological lab (GIA, IGI, AGS)
- Describes physical characteristics: 4Cs, proportions, fluorescence
- No monetary value included — ever
- Permanent record linked to the stone via laser inscription
- Cost: $50–$200 depending on size, lab, and report type
- Used for: buying, selling, verifying, comparing stones
What the diamond is worth
- Issued by a certified appraiser (GIA Graduate Gemologist, ASA, AGS member)
- States a dollar value for a specific purpose (insurance, estate, divorce)
- Insurance appraisals are set above retail replacement cost — not resale value
- Requires periodic updates as market prices change
- Cost: $50–$150 per stone, or hourly rate
- Used for: insurance coverage, estate, divorce proceedings, resale reference
Insurance appraisals are typically 50–100% above what you paid. This is intentional — replacement cost accounts for retail markup, setting, and future price changes. Do not confuse an appraisal value with resale value. A diamond appraised at $8,000 might sell for $2,000–3,000 on the secondary market.
Red flags to watch for
Report from an unknown lab
Many regional labs grade loosely or inconsistently. If you've never heard of the lab, look it up and search for reviews. Some labs exist primarily to issue inflated certificates. Stick to GIA, IGI, AGS, or HRD for significant purchases.
No laser inscription
GIA inscribes all reports. No inscription on a supposedly GIA-graded stone is a major red flag. Verify the stone through a loupe — the inscription is on the girdle, readable at 10×.
Inscription doesn't match report
If the number on the girdle differs from the certificate, the stone has been switched. This is the most common form of diamond fraud. Walk away immediately.
Report not in database
If the lab's online lookup returns no result for a report number, or returns different grades, the certificate is either fake or has been tampered with.
Seller discourages verification
Any reluctance to allow you to verify a report independently — "the system is down", "it's a new report", "trust me" — is a serious warning sign.
Appraisal instead of lab report
A seller offering an appraisal (dollar value document) instead of a lab grading report is not the same thing. An appraisal does not independently verify grades — it is just one person's opinion.
Questions about grading reports
Do I need a grading report to buy a diamond?
For any diamond above 0.30–0.40 ct, yes — a report is essential. Without one, you are relying entirely on the seller's description of a stone's quality, with no independent verification. Below 0.30 ct (melee, accent stones) reports are typically not economical — the grading cost approaches the stone's value — so these are often sold without reports and priced accordingly. The two most trusted labs are GIA and IGI.
Can a grading report be faked?
Yes, but verifying one is straightforward. Enter the report number at the issuing lab's website — GIA Report Check, IGI Verify, and similar tools are free and public. A genuine report will return matching grades in the database. Also check the laser inscription on the stone's girdle under a loupe — the number must match. Physical certificates have security features (hologram, microprint line on GIA reports) that are difficult to reproduce convincingly.
What is the difference between a certificate and a report?
Labs prefer "report" because "certificate" implies a guarantee of value — which they do not provide. A grading report is a factual statement of characteristics, not a promise about what the stone is worth. That said, in common usage "certificate" and "report" are used interchangeably. The important distinction is between a lab report (independent) and an appraisal (a dollar-value opinion from an appraiser, typically for insurance).
Why doesn't a grading report include a price?
By policy and principle. Labs are independent graders — their job is to describe the stone objectively. Including a price would create a conflict of interest (labs might be pressured to inflate grades to support higher prices) and would also be inaccurate (prices change constantly; a report may be used for years). For current benchmark prices, use DiamondTheGuide. For insurance replacement value, you need a separate appraisal from a certified appraiser.
What is a laser inscription and why does it matter?
GIA (and some other labs) laser-inscribe the report number on the diamond's girdle at microscopic scale, readable under a 10× loupe. This permanently links the stone to its report. It is the most important anti-fraud feature — it means a seller cannot switch a stone and hand you a mismatched certificate. Always verify the inscription matches the report number before completing a purchase.
Should I get a diamond re-graded?
Consider it if: the report is from a lab with loose grading standards (some regional labs); the report is very old (10+ years) and you want to know the current standard-equivalent grade; you are selling the stone and want a GIA report to support the asking price; or the existing report is damaged or lost. Re-grading costs $50–$150 depending on size and lab, and the stone must be unmounted. Budget for the possibility that a re-grade may come back at a lower grade than the original, especially if the original report was from a less rigorous lab.