GIA is among the best grading labs for diamonds in the world. The consistency with which it grades stones is renowned, so much so that it’s considered the standard-bearer when it comes to diamond certification in the industry. When retailers show diamond rings, they also give you some information about diamond characteristics, usually on a certificate.
Meanwhile, you also have IGI, or the International Gemological Institute, a large institution that also grades and certifies diamonds, and has been doing since 1975. Both of these labs are reputed institutions, but GIA does trump IGI in certain respects when it comes to certification.
A Preview Of GIA and IGI
GIA, founded in 1931, is dedicated to natural gemstone research, grading, and education. It developed a standard to enable everyone to use a unified methodology for diamond grading, called the International Diamond Grading System. It has 9 laboratories and operates in 13 countries.
The IGI is an independent gem lab (the largest in the world), with its HQ in Antwerp. It has offices in many diamond centers such as New Delhi, New York, Dubai, and Tel Aviv. It employs over 650 gemologists as well as other jewelry professionals.
The Difference Between GIA and IGI
GIA is the go-to lab for grading diamonds in the US, while IGI mainly operates in Europe and Asia. The latter is not as strict when grading diamonds as the former, but that’s not to say you should rule out an IGI certificate right off the bat, especially when buying shaped wedding rings with diamonds.
What To Expect
IGI has a loose structure globally, which means there can be slight inconsistencies among grading from the different labs under it. Generally, you can assume a single grade color inconsistency when it regards D through I color diamonds, as compared to GIA certified stones. There would also normally be a single grade clarity inconsistency between GIA and IGI graded stones, especially in stones landing between the D and F colors, as well as VVS to flawless clarity.
It’s very important to be on the same page as the retailer before a purchase, as well as, inquire about the clarity levels of SI1 and SI2 graded diamonds (IGI). This is because such stones may not be eye-clean. As a customer, it’s your responsibility to ensure that any low-clarity ISI graded stones you buy are indeed eye-clean, and have no obvious inclusions.
All of the above aside, up to a fifth of IGI graded diamonds can end up being consistent with GIA grading. This is because of the simple fact that it is human beings that do the grading in both institutions, and sometimes, the gemologist grading at IGI is just as strict as the one that did it at GIA.