European Gemological Provides diamond, colored stone and pearls certification, analysis and consultations. http://www.eglusa.com/
Gemological Institute of America The world’s largest and most respected nonprofit institute of gemological research and learning. http://www.gia.edu
International Gemological Institute The world's largest independent gem certification and appraisal institute and is renowned for its quality services, extensive experience and know-how. http://www.igi-usa.com/