Emerald is part of the beryl group of gems, and is among the four traditional precious stones, the others being sapphire, ruby, and diamond. It is the most precious stone in the beryl group.
The emerald is a fragile stone because of its many natural inclusions. The color of the emerald is the most important factor when determining value. The most popular and valuable color is a slightly bluish green in a medium dark tone with strong to vivid saturation. An emerald definitely looks best in daylight, but artificial light will indeed expose all inclusions that absolutely prove the stone to be natural. So, it is best to test it out in both types of light. This being said, inclusions in emeralds, unlike in most any other gemstone on earth, are preferred and add more value to the stone.