em·er·ald | ˈem-rəld
A gemstone of the beryl family
Fine emeralds are among the most valuable gemstones. Unlike most gemstones, flaws (called "inclusions" by gemologists) are quite common in emeralds, so they lower the value much less than with other precious stones, such a diamonds.
The most highly prized emeralds are mined in Colombia. A valuable emerald will be a bright, vividly colored green. Those with a slight blue cast to the bright green are the most valuable color.
Many emeralds seen in jewelry are of relatively low quality. They are often dyed or oiled to improve the color and minimize flaws. If an emerald appears to be very fine, it may be a synthetic. There are several types of synthetic emeralds on the market, and some of them are challenging to identify, even for a trained gemologist.