Emerald

The green to bluish green variant of the mineral species known as beryl, which also contains the aquamarine gemstone and beryls in various hues, is emerald.

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Emeralds are rated using the 4 fundamental criteria—the four Cs of connoisseurship—as are other colored gemstones: color, clarity, cut, and carat weight. In grading colored gemstones, color is typically by far the most significant factor. However, clarity is ranked as a close second in the grading of emeralds. For an emerald to be regarded as a top gemstone, it must have a high degree of transparency in addition to a clean, lush green tint.