IGI certified lab grown diamonds come with a grading report from the International Gemological Institute, the lab whose paperwork you will see most often on lab diamonds. The report is your proof of what you are buying: that the stone is laboratory grown, and exactly how it grades for cut, color, clarity and carat. This guide shows you how to read an IGI report line by line, how to check that it matches your stone, and how it compares with a GIA report.
What “IGI certified” really means
People say “certified,” but what you actually get is a grading report. An independent gem lab examined the diamond, measured it, graded it and wrote the results down with a unique report number. The lab does not sell the stone and has no stake in the price, which is what makes the report useful.
Every lab grown center stone we offer comes with an IGI or GIA report. If a stone has no report from a known lab, you are relying on the seller’s word alone. For a diamond you will wear every day, that is not enough.
How to read an IGI report, section by section
IGI reports follow a clear layout. Here is what each part tells you:
| Section | What to look for |
|---|---|
| Report number | A unique number. It should match the inscription on the stone. |
| Description | Should say laboratory grown diamond. |
| Shape and cutting style | Round brilliant, oval brilliant, emerald cut and so on. |
| Measurements | Length, width and depth in millimeters. Useful for comparing face up size. |
| Carat weight | The weight to two decimals. |
| Color grade | Letter grade, D is colorless. |
| Clarity grade | From FL down to I3. |
| Cut grade | Given for round brilliants. Fancy shapes may not have one. |
| Polish and symmetry | Finish quality. Excellent or Very Good is what we look for. |
| Fluorescence | How the stone glows under UV light. None or faint is common. |
| Comments | Notes on the growth method and any treatment after growth. |
| Inscription | What is laser written on the girdle, usually the report number. |
Most reports also show a plotted diagram of the inclusions and the stone’s proportions. The plot is handy at the showroom: find a mark on the diagram, then find it in the stone under the loupe. If you need a refresher on the grades themselves, read our plain words guide to the 4Cs.
The comments line: growth method and treatment
The comments section is easy to skip, but read it. It usually says how the diamond was grown, CVD or HPHT, and whether it had any treatment after growth to improve its color. Post growth treatment is common in lab diamonds and is not a defect. It is part of how many lab stones reach a white color. What matters is that it is disclosed, and on an IGI report it is. Our page on CVD vs HPHT explains what the two methods mean for you.
How to check a report against the stone
A report is only useful if it belongs to the diamond in front of you. Checking takes a few minutes:
- Read the inscription. Under a 10x loupe, look at the girdle, the thin edge around the stone. Most lab diamonds carry the report number there in tiny letters.
- Match the number. The inscription should match the number printed on the report.
- Look it up online. Enter the number on IGI’s own report check page. The grades and measurements shown should match the paper.
- Measure if you can. A jeweler can measure the stone’s length and width. They should match the report within a hair.
IGI vs GIA for lab grown diamonds
Both IGI and GIA grade lab grown diamonds, and both are well known names on 47th Street. IGI is the report you see most often on lab diamonds, which makes it easy to compare stones across sellers. GIA also grades lab grown diamonds, and the type of report is printed on the paperwork itself.
In practice, our advice is simple. Compare stones on the same lab’s report whenever you can, because grading styles differ a little between labs. Do not choose a stone on the report alone. Two stones with the same grades on paper can look different in person, especially in fancy shapes where cut has no single grade. If you tell us you prefer one lab, we will pull stones with that report for your visit.
Keep the report safe after you buy
The report is worth keeping long after the ring is on your hand. Your insurer will usually ask for it, along with the receipt. A jeweler will use it to confirm the stone if the ring ever goes in for sizing, cleaning or a new setting. Keep the paper somewhere dry, take a photo of both sides, and save the report number in your phone. If the paper is ever lost, the number still lets you look up the grades online.
Questions worth asking about any report
- Is the report from an independent lab, and can I look up the number myself?
- Does the description clearly say laboratory grown?
- What does the comments line say about growth and treatment?
- Is the inscription on the stone, and does it match?
- For a fancy shape, what are the length, width and depth, and how does it look face up?
A seller should be glad to answer each one. If the report is missing, unclear, or from a lab you cannot look up, walk away or ask for a different stone.
Request IGI or GIA graded stones for your visit
Our loose lab grown diamonds page lets you choose shape, carat range, color, clarity, budget and report, IGI or GIA. We pull 3 to 5 matching stones, each with its report, and have them on the tray when you arrive. You can also browse lab grown diamond engagement rings to choose a setting first.
The showroom is at 30 West 47th Street, Suite 806, between 5th and 6th Avenue, two blocks from Rockefeller Center. Book a viewing or call (212) 642-4345.
Viewings by appointment. Tell us what you would like to see and we will have it out on the tray.
Book a viewingOr call (212) 642-4345