Who is who
- GIA (Gemological Institute of America) is a nonprofit institution founded in 1931 in the United States. It created the D-Z color scale and the clarity scale the whole industry uses. Its report is the most recognized for natural diamonds.
- IGI (International Gemological Institute) was founded in 1975 in Antwerp and has laboratories in the main cutting centers. It certifies natural stones, but it is the dominant laboratory for lab-grown diamonds and finished jewelry.
What both of them grade
Both reports describe the 4Cs (carat, color, clarity and cut), measurements, fluorescence, symmetry and polish, and include an inclusion plot. For lab-grown diamonds they also state the growth method (HPHT or CVD) and any post-growth treatment.
Differences that actually matter to a jeweler
| GIA | IGI | |
|---|---|---|
| Main use | Natural diamonds | Lab-grown diamonds and finished jewelry |
| Reputation for strictness | Market reference for natural | Broad and accepted; some buyers consider it slightly less strict on color and clarity |
| Availability in lab-grown | Lower | Very wide |
| Online verification | GIA Report Check | IGI Verify Your Report |
| Girdle inscription | Yes | Yes |
Which one to choose depending on what you sell
- Natural engagement or investment diamond: GIA. It is what the end customer knows and what makes resale or appraisal easier.
- Lab-grown diamond: IGI is the standard and offers the widest selection; GIA is also available if the client asks for it.
- Finished jewelry with many stones: IGI, because it certifies the whole piece.
- Melee: not certified individually; bought by calibrated lot. See the calibrated melee guide.
How to verify a certificate
With the report number you look it up on the laboratory's website and compare it with the stone: weight, measurements and the laser inscription on the girdle, visible with a 10x loupe. At Bamo we verify every certificate before quoting. See how to buy by certificate number.