GIA first put forward the concept of 4C systematically in 1930s, and formally established the system in 1953, and put forward the rules of diamond 4C classification.
Colors from D to Z represent the grades of colors from light to dark in turn, and the colors are divided into 23 grades, replacing the original old terms and color division.
The definition of each clarity level is defined, and the clarity is divided into 1 1 level, which is more detailed than the European level. Some phenomena or defects that are considered as external characteristics in other diamond classification rules are regarded as inclusions, so the role of these characteristics is tested in the evaluation of clarity grade. Especially in the evaluation of FL clarity level, external features play a very important role.
In the aspect of cutting classification, based on American ideal round drill, the cutting proportion of standard round drill is calculated, and the concept and method of systematic evaluation are put forward.
NGTC (Jewelry and Jade Jewelry Management Center, Ministry of Land and Resources)
China diamond grading standard was issued on July 1 day, 2003, and implemented on June 1 1 day, 2003. The revision was completed on 20 10 and implemented on 20 1 1 February. Mainly refer to the standards of IDC and GIA.
The biggest difference from foreign diamond grading standards is that a simple grading standard is established for inlaid diamonds.
IGI international gem college
Founded in Antwerp, Belgium, the World Diamond Center, 1975, is the world's largest independent gem identification laboratory and gem research and education institution. IGI certificate accounts for 35% of the global jewelry appraisal certificate market, which is equivalent to GIA of American Gemological Institute.
HRD Belgian Diamond High Council
Founded in 1973, it is a non-profit organization of diamond industry and commerce recognized by the government. Provide processing technology, commercial trade, diamond identification and classification, personnel training and other services. , to carry out international exchanges.
Its characteristics are: clear classification and quantification, so as to eliminate human influence and make the results more objective. Although there is a breakthrough, the operability is poor.