Diamonds can be roughly divided into five grades from D-Z, among which D, E and F are the best colorless, D is the best, and E and F are the second. After that, G, H, I and J are suboptimal and close to colorless. After K-Z coloring, k, l, m are yellowish, and N-Z is the worst yellowish.
Extended data:
Before GIA founded the D-Z color grading system, there were many other name grading systems in the market, such as English letters A, B and C (which were not clearly defined when used), Arabic numerals (0, 1, 2,3), Roman letters (I, II and III), and descriptive words such as "sapphire blue" or "blue and white". In view of this, GIA decided to create a brand-new color grading system, which has nothing to do with the earlier system. ?
GIA hierarchy begins with the letter D. Because GIA hierarchy is clear and clear, it is quickly accepted by the public, and other hierarchies are gradually abandoned.
Baidu Encyclopedia-4C Standard for Masonry Appraisal