Emeralds, like all colored gemstones, are graded using four basic parameters–the four Cs of connoisseurship: color, clarity, cut, and carat weight. Normally, in the grading of colored gemstones, color is by far the most important criterion. However, in the grading of emeralds, clarity 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 gemstone.