Something quietly significant happened to lab grown diamond paperwork this year, and most people comparing IGI vs GIA reports have not caught up to it. The two best known laboratories no longer describe a lab grown diamond in the same language at all.

One still hands you a letter for color and a letter for clarity, exactly as the trade has done for decades. The other now hands you a tier. If you are shopping for a lab grown diamond in 2026, that single difference decides how much you can actually compare one stone against another, and it is the reason two reports on two nearly identical diamonds can read nothing alike. Here is what each document now contains, what changed and when, and how to read either one in about five minutes.

Those three numbers explain the whole shift. Trade coverage by Rapaport quotes IGI managing director and chief executive Tehmasp Printer putting the laboratory at a 33% global share of diamond certification overall and 65% in lab grown diamonds specifically, which is why the report in your hand is statistically likely to be an IGI one. In its own announcement, GIA stated that more than 95% of laboratory grown diamonds entering the market fall into a very narrow range of color and clarity. And the category is no longer niche: the 2026 Real Weddings Study from The Knot Worldwide found lab grown center stones in 61% of all engagement ring purchases, a 239% rise since 2020.

What a Lab Grown Diamond Report Actually Certifies

A lab grown diamond report is an independent laboratory's written measurement of one specific stone, not a valuation and not a guarantee of price. It records what the diamond is and, crucially, that it was grown rather than mined. Everything else on the page is detail layered on top of that single identification.

• Identity. The stone is confirmed as laboratory grown, and the growth method (HPHT or CVD) may be noted.
• Measurements. Shape, cutting style, millimeter dimensions and carat weight, all of which are objective and machine measured.
• Quality description. Either graded color and clarity, or a broad quality tier, depending on which laboratory you are reading.
• Craft. Polish and symmetry, and a cut grade where the shape allows one.
• Traceability. A report number, usually matched to a laser inscription on the girdle so the paper and the stone stay married.

If that first line is the one that catches your eye, our guide to CVD versus HPHT growth explains what each method actually involves and why the report matters more than the machine.

Roomy's pieces are built on lab grown diamonds carrying IGI certification alongside our own Roomy's certification, and every finished piece is set in solid 10, 14 or 18kt gold. The Lumière Pear Diamond Tennis Bracelet (from $6,550) is a useful example of why the paperwork matters on a multi stone piece: two carats of pear cuts have to match each other in color and clarity, not just hit a grade individually.

IGI vs GIA: The Two Reports Side by Side in 2026

IGI still issues full 4Cs color and clarity grades on lab grown diamonds, while GIA now sorts them into two descriptive tiers called Premium and Standard. That is the headline difference, and the table below is the practical version of it.

Neither document is dishonest, and neither changes the diamond. They answer different questions. An IGI report answers how good, precisely. A GIA assessment answers good enough, yes or no. If you are choosing between two stones at the same price, precision is the more useful answer, which is why our lab grown diamond color guide and our clarity guide are both written against graded letters.

What Changed at GIA, and Why It Happened

GIA stopped issuing lettered color and clarity grades for lab grown diamonds on October 1, 2025, replacing them with a printed Quality Assessment. Reporting by National Jeweler set out the thresholds in detail: Premium covers D color with VVS clarity or better plus excellent polish, symmetry and cut grade on round brilliants, Standard covers E to J color with VS clarity, stones that clear neither bar receive no designation, and the assessment is priced at $15 per carat with a $15 minimum.

The reasoning was compression, not disdain. As GIA president and chief executive Pritesh Patel put it in coverage by JCK, "Using descriptive terms for the quality of laboratory-grown diamonds is appropriate, as most fall into a very narrow range of color and clarity." When almost every stone in a category lands in the top slice of a scale built for a much wider natural range, the scale stops discriminating between them. GIA's answer was to stop using it.

How to Read an IGI Certified Diamond Report in Five Minutes

Read an IGI certified diamond report in this order: identity, weight, cut, color, clarity, then inscription. That sequence moves from the facts that cannot be argued with to the ones that involve a grader's judgement, and it stops you fixating on a single letter.

• 1. Confirm it says laboratory grown. This is the line that defines what you are buying. Everything else is secondary.
• 2. Check carat weight against the shape. A 1.00ct emerald cut and a 1.00ct round look nothing alike face up, because weight hides in depth.
• 3. Read cut, polish and symmetry first. Cut governs how much light comes back. It is the one grade you should not compromise on.
• 4. Then color. In a yellow gold setting, a G or an H reads white to the eye and spends less of your budget than a D.
• 5. Then clarity. Eye clean is the practical bar. VS2 is eye clean in the overwhelming majority of stones.
• 6. Match the inscription. Report number on paper, report number on the girdle. If they differ, stop.

That framework is why a well chosen $700 piece and a $6,000 piece can both be honestly certified. The Linear Diamond Half Eternity Band (from $700) spends its budget on a clean line of matched small stones. The Duet Diamond Bypass Ring (from $1,150) spends it on two larger diamonds where individual grades matter more. The Starlight Portal Diamond Stud Earrings (from $1,500) need matched pairs, which is a sourcing problem before it is a grading one.

Where the Certificate Stops Mattering

A certificate cannot tell you whether a piece is well made, and that is the limit worth understanding. Grading laboratories measure stones. They do not measure whether prongs were finished by hand, whether a bracelet's links articulate smoothly, or whether the gold is solid rather than plated.

This is where our own Roomy's certification sits alongside the IGI report: setting quality, metal karat and finish, judged on the finished piece rather than the loose stone. Compare the Éclat Emerald Diamond Tennis Bracelet (from $500) with the Gloire Round Diamond Tennis Bracelet (from $3,200) and the difference is carat weight and cut demand, not certification. Both are IGI certified. Only one is carrying 1.19 carats of round brilliants across the wrist.

And once you know how to read the paperwork, the more enjoyable question is what to do with the stones: our edit on cocktail rings for 2026 looks at the sculptural statement pieces those certified diamonds end up in.

Frequently Asked Questions