Certified diamonds are graded in laboratories using certain criteria. Some of the most common grading labs include the Gemological Institute of America (GIA) and the International Gemological Institute (IGI). These labs are independently run and provide an expert opinion on quality for loose or unset gems. Most grading institutes have labs or services worldwide and do not sell diamonds. Two types of reports are available: (1) Full Certificates provide full details about a stone including clarity, symetry and polish, and (2) Color-only certificates that provide color grading for natural fancy colored diamonds.

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