Diamond Certificates: GIA and IGI Explained

The word "certificate" is what shoppers say. The labs call it a grading report, and that name is more honest. A report tells you what a grader measured and saw on one specific stone on one specific day. It does not tell you what the stone is worth, what you should pay for it, or whether the ring around it is well made.

A report is useful for three things:

• Identity. It ties a loose diamond to a report number, and often to a laser inscription on the stone's edge, so you know the stone in front of you is the one described.
• Grades. It records the 4Cs: carat weight, color, clarity and, for some shapes, cut.
• Origin. It states whether the diamond is natural or laboratory-grown, which the FTC requires sellers to disclose clearly.

That last point matters more every year. Lab-grown and natural diamonds look the same to the eye and test the same on a basic tester. The report, and a lab's ability to identify origin, is how buyers and jewelers keep the two straight. Our guide to lab vs natural diamonds covers what the origin difference means for price.

Two labs dominate what a US buyer will see in a store or online. Here is how they compare on the points that affect a purchase.

Point	GIA	IGI
Who they are	Gemological Institute of America, a nonprofit that created the 4Cs grading language	International Gemological Institute, a commercial lab with locations worldwide
Where you see it most	Natural diamonds, especially larger center stones	Lab-grown diamonds; IGI grades most lab-grown stones sold today
Natural diamond report	Full D-to-Z color, FL-to-I3 clarity, cut grade on round brilliants	Full color and clarity grades, plus cut grade
Lab-grown report (2026)	Laboratory-Grown Diamond Quality Assessment: "premium" or "standard", no letter grades	Full color, clarity and cut grades, growth method and treatment comment
Online check	GIA Report Check, by report number	IGI's online report verification, by report number
Reputation on color and clarity	The reference standard the trade measures against	Widely accepted; traders often judge it a little more generous on color and clarity

The last row is a trade opinion, not a published fact, and it varies stone by stone. The practical takeaway: compare an IGI-graded stone with other IGI-graded stones, and a GIA-graded stone with other GIA stones. Cross-lab comparisons on one letter grade are not apples to apples. The full head-to-head lives on our GIA vs IGI comparison.

GIA's natural diamond grading report is the document most buyers picture. For a natural stone it records:

• Report number and date of issue
• Shape and cutting style, such as "round brilliant" or "pear modified brilliant"
• Measurements in millimeters, length by width by depth
• Carat weight to the hundredth
• Color grade on the D-to-Z scale and clarity grade on the 11-step scale from Flawless to I3
• Cut grade, for standard round brilliants only
• Polish, symmetry and fluorescence
• A plotted diagram showing where the inclusions sit, on the full report
• Any laser inscription on the girdle

The clarity grade and plot are worth reading together. Two stones can both be graded VS1 with the inclusion in very different places. One near the edge, under a prong, disappears once set. One under the table, the big top facet, is easier to find with a loupe. Our diamond clarity chart explains every grade on that scale.

Fancy shapes like pear, oval and emerald do not get an overall GIA cut grade. They get polish and symmetry grades, and you judge the rest with your eyes: brightness, the size of any bow-tie, and how the outline looks.

On natural diamonds the lab name is part of the price. Two stones with the same carat and the same letter grades can be priced apart because one is graded by GIA and the other by a lab the market sees as softer. Buyers pay for confidence that "G" really means G.

On lab-grown diamonds, the price gap between labs is smaller because the stones themselves are less scarce and cost less to begin with. Here the report's job is mostly to confirm origin, weight and grades so you can compare offers fairly.

Use these rules of thumb:

• Comparing natural stones above about 1 carat: a GIA report is the most widely trusted benchmark.
• Comparing lab-grown stones: IGI reports are the most common, and comparing IGI to IGI keeps things fair.
• A stone graded by a lab you have never heard of: treat the grades as a claim, not a fact, and price it as if it were a grade or two lower until you see it.

None of this replaces looking at the stone. The report narrows the field; your eyes make the final call. The VVS diamonds guide shows why a higher clarity grade on paper often looks no different on the hand.

This is the change most older articles miss. On 1 October 2025, GIA replaced its lab-grown diamond grading report with a Laboratory-Grown Diamond Quality Assessment. Instead of a D-to-Z color letter and a VS-style clarity grade, a qualifying colorless or near-colorless lab-grown stone is now described as "premium" or "standard". Stones below GIA's threshold get no descriptor at all.

GIA's stated reason is that the vast majority of lab-grown diamonds entering the market fall in a narrow band of color and clarity, so fine letter grades add little information. The girdle of an assessed stone is inscribed with "Laboratory-Grown" and the assessment number.

What it means for you:

• A lab-grown stone advertised with a GIA letter grade such as "E VS1" was graded before that date, or the grade came from another lab.
• If you want a lab-grown stone with a written color and clarity grade, an IGI report is the common route in 2026.
• Natural diamond reports from GIA did not change. They still carry full color and clarity grades.

More background on how lab stones are made and identified is in our lab-grown diamonds guide.

A report is only worth something if it matches the stone. Run this check before paying for any graded diamond.

1. Get the number. Ask for the report itself or a photo of it, not just the grades typed into a listing.
2. Look it up. GIA numbers go into GIA Report Check on gia.edu. IGI numbers go into the verification page on igi.org. Both are free.
3. Match every field. Shape, carat to the hundredth, measurements to the hundredth of a millimeter, color and clarity should all match the paper. A carat weight that is off by a few points is a red flag.
4. Check the inscription. If the report lists a girdle inscription, ask to see it under 10x magnification. The number on the stone should match the number on the report exactly.
5. Read the origin line. "Laboratory-Grown" on the report or the girdle means lab-grown, whatever the listing says.

Not every stone carries an inscription. It is an optional service on many natural reports. When there is no inscription, measurements are your best match: they are recorded to the hundredth of a millimeter and are hard to fake on a different stone.

A laser inscription is a line of tiny characters written on the girdle, the thin edge around the widest part of the stone. It is far too small to see with the naked eye and does not affect how the diamond looks or its clarity grade. Under a 10x loupe it reads as a clean line of letters and numbers.

What can be inscribed:

• The report number, so the stone and the paper can always be matched
• "Laboratory-Grown" or "LG", on lab stones from GIA and IGI
• A brand logo or a personal message, on request from some labs

The inscription is the fastest way to confirm a stone after it leaves the store: when it comes back from cleaning, when you get an appraisal, or when you insure it. Write down the inscription at purchase and keep it with your receipt and a copy of the report. If a stone has no inscription, the report's measurements become your fingerprint, so keep those too.

An inscription can be polished off, but doing so takes weight off the stone and leaves a trace an expert can spot. A missing inscription that the report says should be there is a reason to stop and ask questions.

A lot of buying mistakes come from expecting the report to answer questions it never claims to answer.

The report does not cover	Why it matters	How to check it instead
Price or value	Two stones with the same grades can sell far apart	Compare several stones with the same lab, shape and grades
The setting and metal	A great stone in a weak setting is a risk	Read the karat stamp and inspect the prongs
Side stones and pavé	Small stones in a band are rarely graded individually	Ask for total carat weight and stone origin in writing
How it looks to you	Bow-tie, brightness and spread vary within one grade	See it in person or on video in daylight
Damage after grading	A chip after the report date is not recorded	Inspect the stone under magnification at purchase

The side stone point is worth stressing. A ring, pendant or chain can hold dozens of small diamonds. Those are described by total carat weight on the receipt, not by individual reports.

Every house ring at Franky Diamonds is listed with its stone origin and its grades: our 84 house rings are 74 lab-grown and 10 natural diamond pieces, and the inventory grades them E color, VS1 clarity. A few examples with real prices:

• Pear Lab Diamond Ring 5.68 ct, 14K Yellow Gold: 4.01 ct center, $4,500
• Oval Lab Diamond Ring 2.47 ct, 14K White Gold: 2.10 ct center, $3,600
• Emerald Natural Diamond Ring 4.54 ct, 14K White Gold: $8,900
• Round Natural Diamond Ring 4.25 ct, 14K Yellow Gold: $6,000

Whichever store you buy from, ask for the grading report on the center stone before you pay, run the number online, and keep a copy with your receipt. If you want to compare stones side by side, the showroom is at 7900 NW 27th Ave, Unit 506, in Miami; plan the trip on our visit page.