GIA's D-Z color grading system is the most widely used grading standard in the industry. D is the highest color scale of a diamond, which means it is completely colorless. From D to Z, with the deepening of color, the grade of diamonds gradually decreases.

Although the color difference between diamonds is too subtle for non-professionals to distinguish, it will cause great differences in the quality and price of diamonds.

Extended data:

In diamond crystal, carbon atoms are interconnected by tetrahedral bonds, forming an infinite three-dimensional skeleton, which is a typical atomic crystal. Each carbon atom forms a valence bond with the other four carbon atoms through SP3 hybrid orbitals, forming a regular tetrahedron.

Because the C-C bond in diamond is very strong, all valence electrons participate in the formation of valence bond, and there are no free electrons, so diamond is not only hard, but also has a very high melting point and is not conductive. In industry, diamonds are mainly used to make probes and abrasives for drilling, and also used to make high-grade decorations such as hand ornaments with complete shapes, which are very expensive.

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