The exceptional of a Blue Sapphire is determined by using the "4 Cs" – color, readability, reduce, and carat weight. color is the most crucial component, with a desire for vivid, severe blues with out over-darkness. clarity refers to the gemstone’s inner inclusions; the fewer the inclusions, the extra precious the stone. The reduce influences how well the sapphire reflects light, enhancing its brilliance. finally, carat weight affects price, although a well-reduce, smaller stone can be more precious than a larger, poorly reduce one.