How to Read an IGI Lab-Grown Diamond Report, Line by Line

An IGI lab-grown report fits on one page. It reads top to bottom in three blocks: who the stone is, how it grades, and what else the lab noticed. The table below follows that order.

Line on the report	Example of what it says	What to do with it
Report number	Starts with "LG" on lab-grown reports	Look it up on igi.org; it must match
Description	"Laboratory Grown Diamond"	Confirms origin; required disclosure
Shape and cutting style	Pear Brilliant, Emerald Step Cut	Tells you brilliant or step faceting
Measurements	Length x width x depth in mm	Work out the length-to-width ratio
Carat weight	To two decimals, e.g. 3.08 ct	Compare with the listing exactly
Color grade	D to Z letter	D-F colorless, G-J near colorless
Clarity grade	FL to I3	VS1 and better are eye-clean in most shapes
Cut grade	Ideal, Excellent, Very Good	Most useful on round stones
Polish and symmetry	Excellent, Very Good	Finish quality of the facets
Fluorescence	None, Faint, Medium	Glow under UV light
Comments	Growth method and treatment note	Read every word
Inscription	"LG" plus the number on the girdle	Check it at 10x

Start at the top right. The report number is the key to everything else, because IGI keeps a digital copy of every report it issues. Enter the number on IGI's report verification page and you should see the same stone, the same grades and usually a downloadable copy.

Three things make a report suspicious:

• The number returns nothing, or returns a different shape or weight.
• The seller shows only a cropped photo with no number visible.
• The listing grades are better than the report grades. A listing that says "D VVS1" when the report says "F VS1" is the most common version of this.

Keep the report number with your receipt. If the stone ever needs to be identified later, that number, plus the inscription, is how you prove it is yours.

The shape line names the outline. The cutting style tells you how the facets are arranged. "Brilliant" means triangular and kite-shaped facets that throw sparkle, as in round, oval, pear and radiant cuts. "Step cut" means long parallel facets, as in emerald and Asscher cuts.

The measurements line is the most underused number on the page. It reads length x width x depth in millimeters. Two quick calculations tell you a lot:

• Length divided by width gives the ratio. A pear measuring 12.00 x 8.00 mm has a ratio of 1.50. Our guide to length-to-width ratio shows the common ranges by shape.
• Depth divided by width gives depth percentage. A stone that is very deep for its width hides weight underneath and faces up smaller than its carat suggests.

Measurements are also your backup identity check. They are recorded to the hundredth of a millimeter, so a different stone is very unlikely to match all three.

This block uses the same 4Cs language GIA built and the trade uses everywhere. Our 4Cs guide walks through each one with real stones. On an IGI report:

• Carat weight is printed to two decimals. 1 carat is 0.2 grams, so a 3.08 ct stone weighs about 0.62 grams.
• Color is a letter from D to Z. Many lab-grown stones sold today fall in the D to H range.
• Clarity is one of 11 grades from Flawless to I3. VS1 means inclusions are visible under 10x magnification but minor.

A worked example: the Pear Lab Diamond Ring 4.49 ct, 14K Yellow Gold in our showroom has a 3.08 ct center stone graded E color, VS1 clarity in our inventory, and sells for $2,800. Those three grades are exactly the fields you would line up against an IGI report: the weight to the hundredth, one color letter, one clarity grade.

Full reports also name the inclusions the grader found. The words sound alarming but are routine:

• Pinpoint: a tiny crystal that looks like a dot at 10x.
• Crystal: a small mineral or diamond crystal trapped inside.
• Feather: a small internal break that looks white or wispy.
• Cloud: a group of pinpoints too close to see one by one.
• Needle: a long, thin crystal.

At VS1 these are minor by definition. The thing to watch on any grade is a feather that reaches the surface near a corner or point, because that is a spot that can chip.

IGI prints a cut grade on many reports, with polish and symmetry beneath it. Cut matters most on round brilliants, where the proportions that give the best light return are well studied. On fancy shapes, treat the grade as one input and trust your eyes for the rest.

Polish and symmetry describe the finish. Excellent and Very Good are the norm on well-made lab stones. Good or lower on a large center stone is worth a second look.

Fluorescence describes whether the stone glows under ultraviolet light, usually blue. In colorless lab-grown stones it is often listed as None or Faint. It rarely changes how a stone looks in daylight, but a strong rating on a high-color stone is worth seeing in person.

This is the part of a lab-grown report that has no equivalent on a natural report, and the part buyers skip. Read the comments line carefully.

• CVD (chemical vapor deposition): the diamond grew layer by layer from carbon-rich gas on a seed plate.
• HPHT (high pressure, high temperature): the diamond grew from carbon under conditions that copy the deep earth.

Both make real diamond. Neither is better by definition; what matters is the finished grades. The second half of the comment is the important part. Since 2021, IGI has written "As Grown, no indication of post-growth treatment" on untreated CVD and HPHT stones. Stones that were treated after growth, often to improve color, carry a different note, and some reports add a separate "indications of post-growth treatment" line.

A treated stone is still a diamond, but you should know about it and pay accordingly. If the comment line is blank or vague, ask why. The lab-grown diamonds guide explains both growth processes in more depth.

IGI lab-grown stones are usually laser-inscribed on the girdle with "LG" and the report number. You need a 10x loupe to read it. Ask the seller to show you, and confirm it matches the report exactly.

Before paying, run this list:

1. Report number verified on igi.org, every field matching.
2. Description reads "Laboratory Grown Diamond".
3. Carat weight and measurements match the stone, not just the listing.
4. Comment line says "As Grown" or clearly discloses treatment.
5. Inscription seen under magnification.
6. Listing grades are not better than report grades.

Want to understand how IGI and GIA reports differ overall? Read diamond certificates explained and the GIA vs IGI comparison.

Here is how a jeweler would talk through a report out loud. The numbers below are an illustration, not a real stone:

Report LG-number, laboratory grown diamond. Pear brilliant, 11.85 by 7.62 by 4.70 millimeters. 3.02 carats, E color, VS1 clarity. Polish excellent, symmetry very good, fluorescence none. Comment: CVD growth process, as grown, no indication of post-growth treatment. Inscription on girdle.

What that tells you in plain English:

• 11.85 divided by 7.62 is a ratio of about 1.56, a classic teardrop.
• 4.70 divided by 7.62 is a depth of about 62 percent, a normal depth that should face up its full size.
• E color is colorless; VS1 is eye-clean in a pear.
• Very good symmetry means you should still look closely at the outline and shoulders.
• The stone was grown by CVD and not treated afterward.
• The inscription gives you a second way to match it to the paper.

Five minutes of arithmetic like this turns a report from a sheet of grades into a picture of the actual stone. It also tells you which questions to ask before you see it.

IGI keeps a digital record of each report, and many sellers send a PDF instead of a printed card. Either is fine, as long as the online lookup matches. Keep three things together after you buy:

1. The report, or the report number written on your receipt.
2. Your receipt showing the stone origin, carat and metal.
3. Clear photos of the ring from the top and side.

That small file answers almost every later question: insurance, appraisal, or simply proving which stone is yours. If you ever compare your ring to a new listing, pull up both reports and compare measurements first. They are more telling than the grades.

Our lab-grown house rings are listed with center carat, total carat, color and clarity, so you can practice reading a stone before you see its paperwork:

• Radiant Lab Diamond Ring 3.55 ct, 14K Yellow Gold: 3.01 ct center, E VS1, $2,200
• Emerald Lab Diamond Ring 4.88 ct, 14K White Gold: 4.19 ct center, E VS1, $6,800
• Oval Lab Diamond Ring 1.92 ct, 14K White Gold: 1.47 ct center, E VS1, $3,200

Note the two carat numbers. The center carat is the stone a report would describe. The total includes the side stones. When you match a report, use the center figure. The full range of shapes is on our lab diamond engagement rings page.