The clarity of diamonds is usually classified by a magnifying glass with a magnification of 10, and the internal and surface defects of diamonds and their influence on luster are classified into the following categories according to the standards of national inspection in China:
LC，VVS 1，VVS2，VS 1，VS2，SI 1，SI2，P 1，P2，P3*** 10。 Diamonds are divided into five grades: excellent, very good, good and relatively good. P-class drill is also called I-class drill.
Diamonds below grade P are generally not used as gems, so they are generally only classified as grade P, and are no longer classified as P 1\P2\P3.
The grading of diamond color is determined by technicians repeatedly comparing the diamond to be graded with the standard color colorimetric stone in the grading environment of professional laboratories.
The whitest diamond is classified as D (starting with the first letter of the diamond). The color of diamonds is divided into 1 1 grades, which are D, E, F, G, H, I, J, K, L, M and N in turn.
Extended data:
Founder of diamond 4C standard.
Robert M. Shipley, American Gemological Institute of GIA, founder of GIA American Gemological Institute, 193 1 founded GIA in Los Angeles, USA. At first, GIA trained jewelers on how to evaluate wholesale prices through evening classes and correspondence courses. 1953, GIA established the first laboratory; In new york.
Started to publish the diamond appraisal report, and then set up two other laboratories in Santa Monica, California and downtown Los Angeles, officially named the Gem Trade Laboratory. INC (GTL) belongs to GIA for full-time appraisal and appraisal.
GIA is a non-profit organization established with the support of famous American jewelers and celebrities. GIA is an appraisal research institution owned by American jewelers, and its subsidiary GTL provides appraisal services.
GIA's Achievements Up to now, GIA has 14 teaching institutions around the world, providing professional courses in research, sales and appraisal, cultivating high-quality jewelry practitioners, and also contributing to GIA's high reputation in the industry.
Baidu Encyclopedia-Diamond 4c