Emeralds have been among the rarest and most prized jewels since ancient times. Regarded as the birthstone for those born during the month of May and the astrological sign of Taurus, emeralds are mined in Colombia, Brazil, Afghanistan, Russia, Pakistan, India and even in the United States - in North Carolina. Emeralds are the symbol of love, rejuvenation and youth. The Gachala Emerald, mined in Colombia, is among the largest ever found in the world at a whopping 858 carats.
Color is the most important criteria by which to judge an emerald stone, with the most prized and expensive gems a deep, vibrant green. The second most important quality is this gem's transparency or crystal quality. Because there are so few emeralds that are clear and free of inclusions (solid foreign bodies that make the stone look cloudy) you can expect an emerald of high transparency to be quite expensive. If an emerald you are considering for purchase has vibrant color, is clear and is reasonably priced, be careful that someone isn't trying to pass off a manmade emerald as a natural stone.
Deal with only reputable jewelers who can truthfully tell you whether the emerald you are considering has been chemically treated in some way with irradiation, dyeing, coating or heating, as this will reduce the value of the stone. Any inclusions evident in the stone can also weaken it, so ask your jeweler's opinion regarding whether the emerald contains too many or ones that are too deep or can otherwise lessen the stone's value. Most emeralds will be oiled with cedar oil to improve their clarity; be assured, this treatment is not done to mask any flaws.
The next criteria for judging an emerald is the cut. Traditionally, an emerald is cut in a rectangular step-cut. Emeralds can also be cut in other popular shapes, including princess, pear, round, marquis, oval and radiant, which will showcase any stone's brilliance and color. No matter what cut is featured in the emerald under consideration, hold it up to the light and view it from several different angles to make sure that it reflects the light from its surfaces equally well, no matter from what direction it is viewed.
It's a good technique to put several emeralds next to each other while judging color, clarity and cut to determine which one appeals most to you. If you are seeking to purchase an emerald which will stand alone in a piece of jewelry such as a ring or pendant, it's best to purchase a smaller but higher quality stone rather than a larger, inclusion-filled stone that is of lesser quality. If you are going to pair the emerald with other quality gems such as diamonds or rubies, you may be satisfied with a stone of lesser quality that also costs less.