IGI Certificate for Lab Grown Diamonds: A First-Time Buyer Checklist

An IGI certificate for a lab grown diamond is a grading report issued by the International Gemological Institute that documents the stone’s physical and optical properties, including the 4Cs, growth method, and laser inscription number. Every first-time buyer should verify the report number against IGI’s free online database at igi.org before completing a purchase, because a certificate that cannot be confirmed in that database is not a certificate worth trusting.

IGI has graded lab grown diamonds since 2005 and is the dominant certification body for this category. The report it produces is dense with data, and most buyers read only the color and clarity grades, then stop. That habit leaves several fields unchecked that can meaningfully change what you are actually getting. The checklist below walks through each one in the order it matters.

What does the report number on an IGI certificate actually tell you?

The report number is the first thing to check, and it does more than identify the document. For lab grown diamonds, IGI report numbers carry the prefix “LG” followed by a string of digits. That prefix distinguishes the stone from a natural diamond report at a glance.

The same number is laser-inscribed on the diamond’s girdle (the outer edge of the stone). Under a 10x loupe, you can read it directly off the stone and compare it to the number printed on the paper. Any mismatch means the certificate and the stone are not the same object.

Checklist item 1: Confirm the report number begins with “LG.” Checklist item 2: Match the printed number to the girdle inscription before you accept the stone. Checklist item 3: Enter the number at igi.org using the Verify Your Report tool. The full grading details should load within seconds. If they do not, stop.

Which 4C grades on the IGI report actually drive price, and what targets should a first-time buyer set?

The four grades (carat weight, color, clarity, and cut) account for roughly 90 percent of a lab grown diamond’s value. Marketing language like “premium” or “near-colorless” means nothing until you check it against the grades on the report itself.

Color

IGI grades color on the D-to-Z scale, with D being colorless. For lab grown diamonds, D through F is colorless and G through J is near-colorless. Because IGI’s grading calibration tends to run slightly more generous than GIA’s, buyers who want a stone that reads as colorless in most lighting conditions often target D or E rather than F or G.

Clarity

Clarity is assessed at 10x magnification, running from Flawless (FL) down to Included (I3). A VS1 or VS2 grade is generally eye-clean, meaning inclusions are not visible without magnification. VVS2 or better is a safe floor for buyers who want no risk of visible characteristics.

Cut

For round brilliant diamonds, IGI assigns an overall cut grade from Excellent to Poor. Polish and symmetry are graded separately. All three should read Excellent (what the trade calls “3EX”) for maximum light return. A poorly cut D/VVS1 can return less light than a well-cut G/VS2 priced 30 to 40 percent lower.

Checklist item 4: Check color, clarity, and cut grades on the report, not the listing description. Checklist item 5: For round brilliants, confirm cut, polish, and symmetry all read Excellent.

What does the growth method field disclose, and why does it matter?

Near the bottom of the IGI report, the Comments section states the growth method used to produce the diamond: either CVD (Chemical Vapor Deposition) or HPHT (High Pressure High Temperature). Both methods produce diamonds that are chemically, physically, and optically identical to mined stones. Neither method produces a superior stone.

What matters is that the method is disclosed. Some CVD-grown diamonds undergo a post-growth HPHT treatment to improve color, and this treatment should appear in the Comments field. If a seller’s listing does not mention treatment but the report’s Comments section does, that is information worth discussing before you buy.

Checklist item 6: Read the Comments section. Confirm the growth method is stated and note any post-growth treatment disclosure.

Is a full IGI report the same as an IGI card certificate?

No, and the difference is significant. IGI issues two types of documentation for lab grown diamonds.

The full grading report includes the complete 4Cs, a proportions diagram, polish and symmetry grades, fluorescence, growth method disclosure, the clarity characteristics plot (a mapped diagram of inclusions unique to your stone), and the Comments section with any treatment disclosure.

The card certificate (sometimes called a dossier) includes only the basic 4Cs and the inscription number. No proportions data. No clarity plot. No treatment disclosure.

A card certificate cannot tell you whether the cut is mediocre, whether the stone has been treated, or what its actual proportions look like. Lower-quality stones are more likely to come with card certificates precisely because a full report would expose those details.

Checklist item 7: Ask for the full IGI grading report, not the card certificate. If the seller can only provide a card, ask why.

What is the yellow paper, and does fluorescence on the report matter?

IGI prints lab grown diamond reports on yellow paper. Natural diamond reports are printed on white paper. The color distinction is intentional: there should be no ambiguity about what kind of stone you are buying the moment the report comes out of the envelope.

Fluorescence is recorded on the report as None, Faint, Medium, Strong, or Very Strong, along with the color of the fluorescence (usually blue). Fluorescence in lab grown diamonds is less common than in natural stones, but it does occur. Strong fluorescence can make a diamond appear slightly hazy in direct sunlight, though the effect varies by stone. For most buyers, None to Faint is the safest range.

Checklist item 8: Confirm the report is printed on yellow paper (lab grown) not white (natural). Checklist item 9: Check the fluorescence field. None to Faint is generally preferable.

The IGI Certificate Is Your Contract With the Stone

Every other part of the buying process, the listing photos, the seller’s description, the price, depends on the certificate being accurate and verifiable. A report number that loads correctly at igi.org, a girdle inscription that matches it, a full grading report (not a card), Excellent cut grades across all three craftsmanship fields, and a Comments section with no undisclosed treatments: those nine checklist items give you an objective record of exactly what you are buying. When you request documentation from any seller, these nine items are the only checklist you need.

Frequently Asked Questions

Can I verify an IGI lab grown diamond certificate for free without visiting a store?

Yes. Go to igi.org and use the Verify Your Report tool. Enter the report number printed on the certificate, which for lab grown diamonds begins with the prefix “LG.” The full grading record loads within seconds at no cost, and you can confirm every grade without leaving your home or speaking to anyone.

What is the difference between a VS1 and a VVS2 clarity grade on an IGI lab grown diamond report?

Both grades are eye-clean, meaning inclusions are not visible without magnification. VVS2 inclusions are extremely difficult to see even under 10x magnification. VS1 inclusions are minor and still require magnification to find. For most buyers, VS1 is a practical and cost-effective target; VVS2 and above adds price without a visible difference in everyday wear.

Does the growth method (CVD vs. HPHT) affect how a lab grown diamond looks or performs?

No. Both CVD and HPHT produce diamonds with the same chemical composition, hardness, and optical properties as mined diamonds. The difference is in the manufacturing process, not the finished stone. What the growth method field on the IGI report mainly tells you is whether any post-growth treatment was applied, which is the detail actually worth checking.

Why do some IGI lab grown diamond reports look different from others I have seen online?

IGI updated its report format for lab grown diamonds in 2023, including a change to the girdle inscription from “LAB GROWN” to simply the “LG” prefix before the report number. Older reports may show the full “LAB GROWN” text on the girdle image; newer ones will not. Both formats are valid. The key check is whether the report number verifies correctly on igi.org regardless of format.

Is an IGI certificate the same as a price appraisal for insurance purposes?

No. An IGI grading report documents a diamond’s physical and optical characteristics. It does not state a dollar value. For insurance, you need a separate appraisal from a certified appraiser, who will use the IGI report as one input alongside current market pricing to assign a replacement value. Keep both documents together after purchase.