The value of diamonds is defined by the "4C" standard, a series of evaluation criteria that were first officially introduced by the Gemological Institute of America (GIA) in 1973. It has since become the global standard for diamond evaluation and serves as a common language for both diamond industry professionals and consumers. Other international diamond appraisal organizations also adhere to the "4C" guidelines and have expanded on the assessment criteria. For instance, the International Gemological Institute (IGI) builds upon the "4C" standard, placing a greater emphasis on the diamond's cutting craftsmanship and further subdividing it into more refined categories, such as "Ideal Cut."