here are several different systems of diamond grading . The system developed by the Gemological Institute of America (GIA) is most widespread and familiar to stone experts from all over the world. Other well-known grading systems include the system of International Diamond Council of Belgium (IDC or HRD), CIBJO system, and Scandinavian diamond nomenclature (Scan D.N.). Some ancient terms are sometimes used, especially for color description. In Russia, the grading system TU 25-07-1319-77 is used. This handbook primarily deals with the GIA and TU systems. With rare exception, all Non-Russian appraisal systems can be easily converted into one another; however, the conversion of them into the Russian system is ambiguous.