What IGI Certification Means for a Lab Grown Diamond
IGI certification means an independent laboratory has graded the diamond, rather than the seller grading its own stock. The International Gemological Institute examines the stone and issues a report stating its cut, color, clarity and carat weight, identified by a unique report number.
That distinction matters because color and clarity are the two grades most easily overstated. A retailer describing its own diamond as "VS clarity" is making a claim. A retailer supplying an IGI report is making a statement that anyone can check.
What is on an IGI lab grown diamond report
Each field on the report answers a specific question about the stone.
| Field | What it tells you |
|---|---|
| Report number | The unique identifier used to verify the report with IGI |
| Shape and cutting style | For example round brilliant, oval or emerald cut |
| Measurements | Length, width and depth in millimeters |
| Carat weight | The weight of the stone. One carat equals 0.2 grams |
| Color grade | Where the stone sits on the D-to-Z color scale |
| Clarity grade | How visible any internal or surface characteristics are |
| Cut grade | How well the stone is proportioned to return light (round brilliants) |
| Polish and symmetry | The finish quality of the facets |
| Fluorescence | Whether the stone glows under ultraviolet light |
| Origin statement | Confirms the diamond is laboratory grown |
| Growth method | Typically CVD or HPHT, the two processes used to grow diamonds |
Reading the color grade
Color is graded on a scale running from D, which is completely colorless, to Z, which shows a noticeable yellow or brown tint. D, E and F form the colorless range. G to J are near-colorless, and most people cannot distinguish them from colorless once set. Tint becomes progressively easier to see from K downwards.
Shop QSE diamonds are E-F color — the upper part of the colorless range.
Reading the clarity grade
Clarity describes how visible a stone's natural characteristics are under ten-times magnification. The scale runs, from best to lowest: FL (flawless), IF (internally flawless), VVS1 and VVS2 (very very slightly included), VS1 and VS2 (very slightly included), SI1 and SI2 (slightly included), and I1 to I3 (included).
The practically useful threshold is visibility to the naked eye. VS1 and VS2 stones have characteristics that a trained grader finds under magnification but that are not visible to the unaided eye. Shop QSE diamonds are VS1-VS2.
How to verify a report
Every IGI report number can be checked on IGI's own verification tool at igi.org. Enter the number and IGI returns the grading details held in its database. If those details do not match the report you were given, the stone is not the one described.
Many IGI-graded diamonds also carry a microscopic laser inscription of the report number on the girdle, the thin outer edge of the stone. Where present, a jeweler can read it under magnification and confirm it matches the report.
IGI and GIA
Both are established, independent gemological laboratories that grade on the same D-to-Z color scale and FL-to-I3 clarity scale. GIA is the older institution and is most closely associated with mined diamonds. IGI is widely used across the lab grown market and is the certification most lab grown retailers supply. For a lab grown diamond, an IGI report is the standard and expected certification.
Reading the cut grade
For round brilliant diamonds the report carries a cut grade, running from Excellent at the top down to Poor. Cut has a greater effect on how much a diamond sparkles than any other grade, because it determines how much light the stone returns to the eye. A well-cut diamond of a lower color grade will often look brighter than a poorly cut stone of a higher one.
Fancy shapes — ovals, pears, emerald cuts — are not always given an overall cut grade, so for those the polish and symmetry grades, and the proportions in the measurements field, carry more weight.
Fluorescence
Some diamonds glow, usually blue, under ultraviolet light. The report grades this from None through Faint, Medium and Strong to Very Strong. In most stones fluorescence has no visible effect in ordinary light. Occasionally, very strong fluorescence can make a stone look slightly hazy. For most buyers it is a minor consideration rather than a deciding one.
Carat weight is not size
Carat measures weight, not how large a diamond looks. Two stones of identical carat weight can appear different sizes depending on how they were cut — a stone cut too deep carries weight in its base where it cannot be seen from above. That is why the millimeter measurements on the report are worth reading alongside the carat weight. As a reference point, a well-cut one carat round brilliant typically measures around 6.4 to 6.5mm across.
What certification does not cover
A grading report describes the diamond. It does not value it, and it does not cover the setting, the metal or the craftsmanship. Those are covered by the retailer's own warranty and returns policy, which is why it is worth checking both.
Every lab grown diamond sold by Shop QSE is IGI certified, graded E-F color and VS1-VS2 clarity, and backed by our lifetime manufacturing warranty and 30-day returns on eligible pieces.
Common questions
What does IGI certified mean?
It means the International Gemological Institute, an independent laboratory, has graded the diamond's cut, color, clarity and carat weight and issued a report with a unique number — rather than the seller grading its own stone.
How do I verify an IGI certificate?
Enter the report number on IGI's verification tool at igi.org. The grading details IGI holds are returned and should match your report. Many stones also carry a laser inscription of the report number on the girdle.
Is IGI or GIA better for lab grown diamonds?
Both are independent laboratories using the same color and clarity scales. IGI is widely used across the lab grown market and is the certification most lab grown retailers supply.
What do E-F color and VS1-VS2 clarity mean?
E-F is the upper colorless range of the D-to-Z scale. VS1-VS2 means characteristics are visible only under ten-times magnification, not to the naked eye.
Does an IGI report tell me what the diamond is worth?
No. A grading report describes the stone's characteristics. It is not a valuation and does not cover the setting or metal.