Diamond grades are divided :

  1. Carat weight, diamond color grade, diamond clarity, diamond turn ratio, and symmetry, polishing, and fluorescent  seven points
  2. Carat, Color, Clarity, Turner Cut" is called "Diamond 4C"

(1) Clarity

At ten times magnification, Accroding to Size, quantity, location, visibility and essencedetermine the appearance and clarity of the diamond.

FL Flawless Flawless, observed with a 10x magnifying glass, without any clarity characteristics.
FL / IF Internally Flawless The highest level of diamonds. The surface features are minimally observed with a 10x magnifying glass.
VVS1, VVS2 Veryvery slightly included  In addition to the ideal FL/IF, the practical clarity of the diamond grade is the highest, quite clear.
VS1, VS2 Very slightly included Diamond clarity VS2, VS1 or more, impurities are not visible to the naked eye, 10x magnifying glass is not easy to detect.
SI1, SI2 Slightly included Diamond clarity SI1, SI2, impurities are not easy to see with the naked eye, 10x magnifying glass is easy to see.
lq , l2 , l3 Imperfect Impurities are visible to the naked eye.


(2) Color
   
The color of the diamond will vary depending on the trace elements contained. The color of the diamond is an important element that affects its value. The white diamond with the highest level of coloration should be transparent and colorless. GIA diamond color grade D is the whitest, the whiter the better. It is recommended to choose the diamond color D, E, F, G, H

Colorless D、E、F
Nearly colorless G、H、I、J
Light yellow K、L、M
Very light yellow O、P、Q、R



(3) Carat
    One carat is equivalent to 200 mg (0.2 g) by weight. One carat can be subdivided  to100 points for the calculation of finer diamonds; therefore, a 30-point diamond is 0.3 carats (0.06 grams) and a 50-point diamond is 0.5 carats (0.1 grams)

Carat
Carat 2.0ct 1.0ct 0.7ct 0.5ct 0.4ct 0.3ct 0.2ct
Weight 0.4g 0.2g 0.14g 0.1g 0.08g 0.06g 0.04g

Diameter
(mm)

near 
8.1
near 
6.0
near
5.5
near
5.0
near
4.5
near
4
 near
3.5
 

(4) Cut
​    "Diamond 3Excellent" , Proportional, polished, symmetrical is close to the perfect proportion of the workmanship, the brightness and the diamond ratio is the best in the workmanship.


(Source: GIA China official website https://4cs.gia.edu/zh-cn)