Emeralds, like all colored gemstones, are graded using four basic parameters the four Cs of Connoisseurship: Color, Cut, Clarity and Crystal. Crystal is simply used as a synonym that begins with C for transparency or what gemologists call diaphaneity. Jewelers used to use the term water as in "a gem of the finest water to express the combination of two qualities, color and crystal. In the grading of colored gemstones, color is by far the most important criterion, however, in the grading of emerald, crystal is considered a close second. A fine emerald must possess not only a pure verdant green hue as described below, but also a high degree of transparency to be considered a top gem. Emeralds, emerald sale, overstock emeralds, colored gemstones, emerald connoisseurship, emerald cut, emerald clarity, emerald crystal, emerald transparency, emerald diaphaneity.