The International Gemological Institute was established in1975 and is headquartered in Antwerp – one the key centers of the diamond business. IGI has several branches all around the world and is one of the largest labs in the world. It also has a gemology school. Since IGI is so big,their labs in different countries seems to be using slightly different criteria while grading diamonds hence inconsistencies in overall grading results. However,they seem to be improving their overall performance. We would grade IGI asslightly less strict than GIA or AGS. It is a good idea to expect one grade inconsistency while buying IGI diamonds. However, no two diamonds are the same,so generalizing anything when comes to buying diamonds is not a good idea – each case is different and therefore should be treated as such.