The Gemological Institute of America (GIA). http://www.gia.edu/gia-about
Established in 1931, GIA is the world’s foremost authority on diamonds, colored stones, and pearls. A public benefit, nonprofit institute, GIA is the leading source of knowledge, standards, and education in gems and jewelry.*
Perhaps what the GIA is most known for is their diamond grading reports such as the GIA Diamond Dossiers pictured below. Many of the diamonds in the rings and other jewelry I offer come with GIA reports.