Emerald

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mephard

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Emeralds are a variety of the mineral beryl (Be3Al2(SiO3)6,) colored green by trace amounts of chromium and sometimes vanadium.[1] Beryl has a hardness of 7.5 - 8 on the 10 point Mohs scale of mineral hardness.[1] Most emeralds are highly included, so the http://en.wikipedia.org/wiki/Emerald