CutThe most important criteria for the beauty of a diamond is cut. The level of craftsmanship defines how much sparkle, fire and brilliance the diamond shows. But it is much more than that: While nature provides the base material in color and clarity, it is only the ability of a master cutter that reveals the unique beauty of a diamond.
Almost all diamonds have inclusions. However, most of them are in fact so small that you need a microscope to actually see them. Benchmark for grading diamonds is the 10x magnifiying loupe: A loupe-clean diamond has no inclusions visible at 10x magnification. Only beginning with the clartiy grade "SI" may inclusions be visible to the naked eye. However, in most cases only the clarity grades "I1-I3" are so heavily included that it is noticable without a loupe.