The Gemological Institute of America (GIA) has a laboratory named the Gem Trade Laboratory (GTL), which is one of many independent grading and testing labs. These laboratories employ experts in the field of diamond grading. These experts have many years of experience in grading and analyzing diamonds. They go to painstaking lengths to insure that each stone studied is given the appropriate grade. Each stone is analyzed by three different experts to insure its proper grading. The analysis is summed for anyone to review in what is termed a "Diamond Quality Analysis Report" also called a "Certificate".
A certificate conveys the essential information and key characteristics of each individual diamond. Most importantly, each diamond’s value will be heavily influenced by the overall analysis on the certificate. A certificate should mention several key features including: shape and cut, carat weight, proportions, finish, clarity, grade, and color grade. In addition, many certificates will also include comments written by the evaluator and a sketch of the diamond showing the location of imperfections.