What Is an IGI Diamond Certificate?
Certificate Guide • Published July 15, 2026
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An International Gemological Institute grading report provides independent assessment log data for lab-grown diamonds.
An IGI certificate for a lab-grown diamond is an independent grading report issued by the International Gemological Institute.
The report confirms that the examined stone is a laboratory-grown diamond and records important characteristics such as its measurements, carat weight, colour, clarity and finish. Depending on the report and services requested, it may also identify the growth method and post-growth treatments.
Although consumers commonly call the document an “IGI certificate”, IGI grading report is the more precise description. The report records the laboratory’s professional assessment of the diamond at the time it was examined.
It is not a guarantee of future value, a jewellery warranty or a recommendation about how much you should pay.
Quick Answer
What An IGI Report Contains
| Report section | What it tells the buyer |
|---|---|
| Report number | The unique number connected to the assessment |
| Description | Identifies the item as a laboratory-grown diamond |
| Shape and cutting style | For example, round brilliant or oval modified brilliant |
| Measurements | The diamond’s dimensions in millimetres |
| Carat weight | The diamond’s weight |
| Colour grade | Where the diamond sits on the relevant colour scale |
| Clarity grade | The visibility and nature of internal or surface characteristics |
| Cut grade | The assessment provided where applicable |
| Polish | The quality of the polished facet surfaces |
| Symmetry | The alignment and arrangement of facets |
| Fluorescence | The diamond’s reaction to ultraviolet light |
| Proportions | Information such as table, depth and girdle measurements |
| Clarity plot | A diagram showing relevant characteristics when included |
| Comments | Additional observations about origin, growth or treatment |
| Inscription | Wording or report number inscribed on the girdle |
1. International Gemological Institute (IGI) Standards
What Is IGI? The International Gemological Institute is an independent gemmological laboratory. It began grading laboratory-grown diamonds in 2005 and has ISO/IEC 17025 accreditation for grading procedures.
Origin Verification: Natural and lab diamonds look identical to the unaided eye. IGI screens stones using specialized machinery to detect growth lines, preventing confusion with natural diamonds or simulants like moissanite and CZ.
.jpg "Origin Verification and Screening")
IGI uses professional screening machinery to distinguish diamond materials from simulants.
2. CVD/HPHT Growths & Post-Growth Treatments
Process Disclosures: Comments on growth processes (CVD or HPHT) and post-growth color treatments are included upon request in the comments section. Treatment does not decrease suitability; it is valuable information that should match the seller's disclosures.
The Grading Steps: Graders measure carat weight (to two decimals), map facet symmetries, compare color hues against reference cards, verify clarity under 10× zoom, and log all data anonymously to prevent bias.
.jpg "Clarity Plots and Growth Comments")
A report highlights clarity characteristics (inclusions) under 10x magnification alongside growth method comments.
3. Laser Girdle Inscriptions and Completed Jewellery Reports
Girdle Inscription: graded lab diamonds receive microscopic laser inscriptions containing the report number. This code can be verified on IGI's website.
Finished Jewellery Reports: Reports for completed rings or necklaces evaluate parameters "as the mounting permits." Claws or bezels block parts of set diamonds, meaning measurements may be estimations.
Accent Melee: In pieces containing many small accent diamonds (melee), only the principal centre stone is individually reported. Product pages should state this clearly.
.jpg "Girdle Laser Inscription Verification")
Verifying the microscopic laser inscription confirms that the physical diamond matches the grading report.
IGI Report Buyer Checklist
| Before ordering a reported stone, verify: |
|---|
| The description confirms origin as laboratory-grown diamond. |
| The unique report number is displayed on the invoice. |
| The report matches IGI’s official database check. |
| Carat weight, millimeter dimensions, and shapes match perfectly. |
| You understand if the report covers loose diamonds or a mounted piece. |
| Precious metal alloy purity and accent specifications are provided. |
Final Verdict
Frequently Asked Questions
What is an IGI certificate for a lab-grown diamond?▼
It is an independent grading report that identifies a stone as laboratory-grown and records characteristics such as carat weight, colour, clarity, measurements and finish.
Is an IGI certificate the same as a valuation?▼
No. A grading report records gemological characteristics and does not normally provide the diamond's retail, insurance or resale value.
Does IGI grade both CVD and HPHT diamonds?▼
Yes. IGI examines laboratory-grown diamonds produced by both methods. Growth-process information may be included in the report comments.
Does an IGI report show diamond treatment?▼
The report may record evidence of post-growth treatment in its comments. Buyers should inspect the specific report supplied.
What is an IGI report number?▼
It is the unique number assigned to the graded item and used to access the corresponding digital report through IGI's verification service.
Where is the IGI number on a diamond?▼
The report number may be laser-inscribed on the diamond's girdle and normally requires magnification to read.
Does every small diamond need an IGI certificate?▼
No. Small accent diamonds are frequently sold without individual reports, but their origin, approximate quality and total carat weight should still be disclosed.
Does an IGI certificate cover the complete ring?▼
Only if IGI issued a finished-jewellery report covering the ring. A loose centre-diamond report does not automatically cover the setting or accent stones.
Can an IGI certificate be fake?▼
Fraudulent documents or copied report numbers are possible. Buyers should verify the report number and ensure the recorded characteristics match the diamond.
Does an IGI certificate guarantee good resale value?▼
No. It documents the diamond's characteristics, but resale value depends on market conditions, demand, condition and the buyer's offer.
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