Emerald

Emeralds are a variety of the mineral beryl, colored green by trace amounts of chromium and sometimes vanadium.. Beryl has a hardness of 7.5 - 8 on the 10 point Mohs scale of mineral hardness. Most emeralds are highly included, so their brittleness (resistance to breakage) is classified as generally poor. The origin of the word "emerald" is said to be a Sanskrit word meaning "green".
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n. emerald

(n.)
A precious stone of a rich green color, a variety of beryl. See Beryl.
  

(n.)
A kind of type, in size between minion and nonpare/l. It is used by English printers.
  

(a.)
Of a rich green color, like that of the emerald.
  

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 Columbia. A valuable emerald will be a bright, vividly colored green. Those with a slight blue cast to the bright green are actually 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 actually 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.