A deep green gemstone. Fine emeralds are among the most valuable gemstones. Unlike diamonds and other precious stones, flaws or inclusions are common in emeralds, so their value is less affected by them than with other precious stones like diamonds. The most highly prized emeralds are from Columbia. A fine emerald is bright, vivid green, with the most valuable having a slight blue cast to the bright green. Many emeralds used in jewelry are of relatively low quality as they are often dyed or oiled to improve the color and minimize the flaws. If an emerald appears to be very fine and lacking any flaws it is most likely synthetic.