The best emeralds are found and mined in Colombia. Color tone and saturation ranging from bluish green or yellowish green. Have a excellent emerald with Excellent luster, transparent eye clarity, medium dark tone and bluish green color is ideal. Emerald is a gemstone and a variety of the mineral beryl colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.58 on the Mohs scale. Most emeralds are highly included, so their toughness is ranged as generally in between.