A diamond has the capability to refract more light than any other gemstone. One which is free of interior inclusions or exterior flaws has nothing to interfere with the passage of light through the stone and so is considered to be of the highest quality. Such stones are very rare and correspondingly expensive!
Most diamonds contain tiny natural marks called inclusions. The number of inclusions, their size and location all affect the diamond’s clarity grade. While it is true that the clearer a diamond, the better, minor inclusions will not compromise a stone’s beauty or endanger its durability.