1. Sapphire has a high hardness, and its Mohs hardness is 9, which is second only to diamond. Although Apple's sapphire hardness is only 6, this hardness value can still effectively protect the mobile phone screen from being scratched and worn in daily use.

2. There is a certain relationship between the hardness and purity of sapphire. Hardness is anisotropic, and there will be different hardness in different directions. The theoretical hardness of pure single crystal sapphire (hexagonal lattice) is Mohs 9, but the actual hardness may be lower than Mohs 9 in some directions due to the influence of impurity ions and stress defects.

To sum up, the hardness and purity of sapphire of Apple mobile phone are within a reasonable range. Although it is lower than the standard sapphire with Mohs hardness of 9, it can still effectively protect the screen of mobile phone from scratch and wear in daily use.