There are four credible laboratories in the United States that specialize in providing qualitative diamond reports: GIA (Gemological Institute of America), IGI (International Gemmological Institute), EGL (European Gemological Laboratory, and AGS (American Gem Society).
The IGI (International Gemmological Institute) is the world’s foremost independent gem laboratory that grades and valuates diamonds. You could call them the “Supreme Court of Diamond Valuation”!
A IGI certified diamond will come with a report that is an unbiased statement of its grade, including size, color, clarity, and proportions (cut) as well as a current retail value.