An emerald is a green beryl, which is a silicate of beryllium and aluminum. The green color of the stone is influenced by the amount of chromium in the silicate. Typical crystal structure is hexagonal in nature and has a hardness between 7.5 and 8. The gem is sometimes found in granite, mainly in pegmatites.
Emeralds are rare, but can be found in Columbia (from the famous Muzo and Chivor mines), Brazil, and East Africa. Prices for fine quality emeralds can exceed the value of diamonds. A top quality Emerald would contain only a few small inclusions not visible to the naked eye. All emeralds do contain some inclusions, which are caused by mica, pyrite, calcite, or other minerals.
Another type of beryl is the blue-green aquamarine. This stone's color is influence by the amount of iron in the silicate, not the amount of chromium, as is the case with an emerald.
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