Emeralds are a variety of the mineral beryl Be3Al2-SiO3-6 colored green by trace amounts of chromium and sometimes vanadium which has been commonly used in fine jewelry for centuries. Beryl has a hardness of 7.5-8 on the 10 point Mohs scale of mineral hardness.
Emerald is regarded as the traditional birthstone for May, as well as the traditional gemstone for the astrological signs of Taurus, Cancer and sometimes Gemini.
In some cultures, the emerald is the traditional gift for the 55th wedding anniversary. It is also used as a 20th and 35th wedding anniversary stone.