The emerald is a gem variety of the colorless mineral beryl. The chemical composition of beryl is aluminum beryllium silicate. The emerald owes its green hue to tiny traces of chromium. The emerald scores 8 on the Mohs scale of hardness.
Flawless emeralds are very rare and most crystals contain small blemishes or mineral inclusions.
Owing to its color, the emerald is the symbol of spring, of fertility, and rain. Some people believe that emeralds have the power to enhance the memory, sharpen the wits, and, when placed under the tongue, can help to predict the future. The emerald has been used as an antidote for poison, a cure for epilepsy, and as a treatment of eye disease, dysentery, and leprosy. The beautiful patterns seen in polished agate slices were caused when microscopic crystals formed in bands and colored deposits as hot, silica-rich solutions filtered through cavities in porous rocks. Valued for its pattern, its toughness also makes it ideal for delicate carving.