Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor.
|Mohs scale hardness||7.5 - 8.0|
|Specific gravity||2.63 - 2.91|
|Refractive Index||1.560 - 1.605|