The GIA, the Gemological Institute of America, is the world's largest nonprofit institute of gemological research and learning. Established in 1931, the GIA originated the famous 4C's of diamond value and is the birthplace of the Diamond Grading System. The GIA color grades of D though Z and clarity grades of IF through I3 are recognized world wide by professional jewelers, diamond dealers and consumers as leaders in the industry. Diamonds with GIA certificates set the standards for diamond pricing.

EGL USA, the European Gemological Laboratory – USA, is one of the largest gemological institutions focusing on gemstone certifications and research for the jewelry trade. Originally part of an international network founded in Europe, EGL USA went independent in 1986 and is no longer affiliated with any other EGL labs outside of the US and Canada. EGL USA has incorporated a new clarity grade of SI3 as a way of identifying the exceptional I1 diamonds. Diamonds with EGL certificates can reflect a 6% lower price from GIA pricing due to borderline cases that receive a higher grade and the use of the SI3 grade which enables diamond pricing to be reconciled with the Rapaport pricing system.

AGS, the American Gem Society, is the world's premier grading laboratory of diamond cut, and offers a cut grade for all fancy shapes and sizes. Established in 1996, AGS has gained the reputation as an industry leader in grading diamond cut. Until 2007, when GIA started grading the cut, AGS was considered the only recognized lab to use for diamonds cut to "Ideal" proportions. Diamonds with AGS certificates can command a 2% premium above GIA pricing because of their tougher standards and superior cut grading system.

The public should be aware that diamond grading is subjective; grades assigned are based on how each individual grader perceives the guidelines. Differences of opinions are discussed within the lab before a final grade is assigned.