Certification
GIA vs IGI Diamond Certificates: Which Report Should You Trust?
Updated: · Vibama Jewels
A diamond report is the only independent proof of what you are buying. Two labs dominate retail diamonds: the Gemological Institute of America (GIA) and the International Gemological Institute (IGI). Here is how to read them and which one to expect for each kind of stone.
Who are GIA and IGI?
GIA is a non-profit institute founded in the United States in 1931. It created the 4Cs grading system and the D-to-Z colour scale that the whole trade uses. Most natural diamonds of meaningful size sold online carry a GIA report.
IGI was founded in Antwerp in 1975 and runs laboratories in many countries, including several in India close to the cutting centres. It grades both natural and lab-grown diamonds and issues the majority of reports for lab-grown stones sold to consumers.
Which report comes with which stone?
| Stone | Report we supply | Why |
|---|---|---|
| Natural diamond, 0.30 ct and above | GIA | The benchmark for natural stones, and the report buyers recognize when reselling |
| Lab-grown diamond | IGI | Widely used for lab-grown stones and fast turnaround from labs near Surat |
| Small side stones and pavé | Not individually graded | Matched by our graders for colour and clarity (F-G, VS) |
GIA also grades lab-grown diamonds. If you want a GIA report on a lab-grown centre stone, ask us before ordering.
What a report tells you
Both labs report the same core facts:
- Origin: natural, or laboratory-grown with the growth method (CVD or HPHT) where known.
- Carat weight to two decimal places.
- Colour grade on the D-Z scale.
- Clarity grade from Flawless (FL) to Included (I3), with a plot of the main inclusions.
- Cut grade for round brilliants, plus polish and symmetry for all shapes.
- Measurements and proportions: table, depth, girdle and culet.
- Fluorescence.
- Treatments: for lab-grown stones, any post-growth treatment to improve colour.
- Laser inscription: the report number engraved on the girdle.
Is one lab stricter than the other?
Trade opinion has long held that GIA is the most consistent grader for natural diamonds. That is one reason natural diamonds with GIA reports often trade at higher prices than stones of the same stated grade from other labs. For lab-grown diamonds, IGI is the market standard and prices are quoted on IGI grades.
What matters most is that you compare like with like: compare a GIA-graded stone with other GIA-graded stones, and an IGI-graded lab stone with other IGI-graded lab stones.
How to verify a report in two minutes
- Ask the seller for the report number and a PDF of the report.
- Enter the number on the lab's official verification page (GIA Report Check or IGI's online verification).
- Check that weight, measurements and grades on the website match the PDF exactly.
- When the stone arrives, view the girdle inscription with a 10x loupe and confirm it matches the number.
We send the report and a video of the exact stone before we take payment for any loose diamond or centre stone, so you can do these checks first.
Red flags
- A "certificate" from the seller's own in-house lab instead of an independent one.
- A report number that does not appear on the lab's website.
- A lab-grown stone sold without the word "laboratory-grown" (or similar) on the report and invoice.
- Grades given only as ranges, such as "G-H, VS-SI", for a centre stone.
Frequently asked questions
Is an IGI report worse than a GIA report?
Not for lab-grown diamonds, where IGI is the norm. For natural diamonds, most buyers and resellers prefer GIA, which is why we supply GIA reports for natural stones.
Does the report affect the price?
Yes. Natural diamonds with GIA reports usually command higher prices than stones with the same stated grades from less strict labs, because buyers trust the grade.
Can a report be faked?
A PDF can be edited, but the lab's online database cannot. Always verify the number on the lab's own site and match it to the girdle inscription.
Do small diamonds come with reports?
Side stones and pavé are too small to grade individually at a sensible cost. We match them in batches for colour and clarity and state the total carat weight and grades on your invoice.