Emerald
Emerald is a gemstone and a variety of the mineral beryl (Be 3 Al 2 (SiO 3) 6) colored green by trace amounts of chromium and/or sometimes vanadium. Beryl has a hardness of –8 on the Mohs scale. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor. Emerald is a cyclosilie