Emerald is the modern and traditional  gemstone for May, sapphire is the mystical gemstone, agate is the ayurvedic gemstone with chrysoprase and beryl being  alternate  gemstones.
      In ancient Egypt, emeralds were mined close to the Red Sea. This tranquil green gem was highly prized by the wealthy and the priest craft. The high cost made it far beyond the average Egyptian's pocketbook.  It's said that Isis wore a green emerald—all who looked upon it were guaranteed a safe trip through the land of the dead. Emeralds in ancient Rome were highly prized and valued for the calming and soothing effects. Nero watched the Roman games in the coliseum through a set of highly prized emerald glasses. With the conquest of South American by the Spaniards in the 16th century, emeralds became more plentiful in Europe.  Pizarro and Cortez subdued the Inca and Mayan civilizations and took over the existing emerald and gold mines and began shipping these captured fortunes of gold and gems back to Spain, who in turn shipped them to India and Philippine trading ports where they found their way to China, Mongolia, and Delhi. These early thefts allowed Spain to become one of the leading world powers at the time.
     Emerald is the birthstone for the month of May. It is also the anniversary gemstone for the 20th and 35th years of marriage.
        Emerald is one of the most highly-prized of all the gems. The name comes from the Greek "smaragdos"which means green stone. The most prized is pure grass green. Emeralds are often characterized by a garden of included crystals trapped within, known as the "jardin", because under magnification you will see all sorts of lovely patterns resembling foliage in a garden. A flawless, clear emerald is very rare and is usually found in only small sizes. Small to medium sized stones are often faceted in the "step" or emerald cut. The gem is also lovely when cut into a cabochon or dome shape. Sometimes emeralds are even carved.
        According to legend, the wearing of emerald not only cured a wide range of ailments, including low I.Q., poor eyesight and infertility, but also enabled the wearer to predict the future.  As part of the normal fashioning process, most emeralds are immersed in colorless oil or resin so small voids are not as noticeable.
        Care should be taken to protect it from scratches, sharp blows, household chemicals, and extreme temperature changes. Do not use a home ultrasonic machine.  Emeralds are found mainly in Colombia, Brazil, Zambia and Zimbabwe.