Emerald, together with aquamarine and beryl, belongs to the beryl group, being the most precious of the group. Its green hue is attributed to trace elements of chrome and sometimes vanadium. The color is very stable against light and heat. Only the finest qualities are transparent, often emerald is clouded by inclusions, these are not necessarily classified as faults, but are evidence of the genuineness of the stone. The most desirable color is a deep green. Emeralds are formed by rising magma and metamorphism. The most important mines are in Columbia. Emerald is the birthstone for May and astrological sign Cancer. Emerald is 7-8 in hardness on the Mohs scale. Most emeralds are oiled to enhance the clarity of the gem. Emerald must be worn with care as can be brittle. Emeralds are considered one of the most treasured gems in the world. Emeralds encourage growth, reflection, peace and balance.