IGI vs GIA for Lab Grown Diamonds: What Changed and How to Read Your Report

Diamond guide · Updated 5 October 2026

What changed at GIA in 2025

On 2 June 2025, GIA (the Gemological Institute of America) announced that it would stop describing lab grown diamonds with the color and clarity grades it uses for natural diamonds. GIA said that more than 95% of lab grown diamonds entering the market fall into a very narrow range of color and clarity.¹ The new system started on 1 October 2025.²

Under GIA's chart, a lab grown diamond is Premium only if it is D color, VVS clarity or better, and Excellent in polish and symmetry (and Excellent cut for rounds). A stone in the E–J color range with VS clarity and Very Good (or Good) finish is Standard. A stone outside both groups gets no GIA assessment at all.³

In practice, a GIA "Standard" lab grown diamond could be E color or J color. Those can look quite different, but the document does not tell you which one you have.

What IGI does

IGI (the International Gemological Institute, founded in 1975)⁴ said in July 2025 that it would keep grading lab grown diamonds on the same 4Cs as natural diamonds, while clearly stating on every report that the stone is lab grown.⁵ An IGI lab grown diamond report gives an exact color grade (D to Z), an exact clarity grade, cut, polish and symmetry grades, measurements, fluorescence, the laser inscription and, where it applies, the growth method (CVD or HPHT) and any post-growth treatment.⁶

IGI vs GIA side by side

Sources: GIA, JCK and IGI (see the list at the end of this guide).

Is IGI as good as GIA?

Both are long-established, independent labs, and both clearly state that a stone is lab grown. For lab grown diamonds today, the real difference is the amount of detail. If you want to know a stone's exact color and clarity, compare two stones, or check that your diamond matches what you paid for, an IGI report gives you those grades. A GIA assessment gives you a group, not a grade.

How to read your IGI report, step by step

1. Report number. At the top. IGI numbers for lab grown diamonds start with "LG", for example LG791617014.
2. Description. It should say "Laboratory Grown Diamond". If it doesn't, ask why.
3. Shape and measurements. For example "Oval Brilliant, 8.00 × 5.70 mm". The size in millimeters tells you how big the stone looks.
4. Carat weight. The weight of the diamond, for example 1.20 carats.
5. Color grade. D, E and F are "colorless"; G to J are "near colorless". Our complete rings use E–F stones.
6. Clarity grade. From FL and IF (flawless) through VVS1, VVS2, VS1 and VS2 down to SI and I. VVS and VS stones usually look clean to the eye.
7. Cut, polish and symmetry. How well the diamond was cut and finished. Look for Excellent or Very Good.
8. Fluorescence. How strongly the stone glows under UV light, from None to Very Strong.
9. Comments. This is where the report states the growth method (CVD or HPHT) and any post-growth treatment, and that the stone is inscribed.
10. Inscription. The report number laser-inscribed on the diamond's girdle (its thin outer edge). It is too small to see without a 10x loupe.

A sample IGI report

Here are the main details from a real IGI report for a lab grown diamond in our diamond list. Use it to practise reading a report, then enter the number at igi.org to see the full report.

What this tells you: F color is colorless, VS1 clarity usually looks clean to the eye, and an Ideal cut grade with Excellent polish and symmetry means the stone was cut to return a lot of light. At 7.4 mm across, it looks like a typical 1.5 carat round. To see what a 1.5 carat ring costs, read our lab grown diamond price guide.

How to check your report online

1. Go to igi.org and open Verify Your Report.
2. Enter the report number from your paper report.
3. Check that the online report matches your paper report: same carat weight, measurements, color and clarity.
4. For the final check, look at the inscription on the stone with a 10x loupe and make sure it matches the report number. Any jeweler can help, or we can show you at our office.

CVD or HPHT: does it matter?

CVD and HPHT are the two ways lab grown diamonds are made. Both produce real diamonds with the same hardness and sparkle. The method alone does not make a stone better or worse, so compare the grades on the report instead: color, clarity and cut.

Questions