Emeralds are a type of beryl and gain their famous green color from chromium and vanadium, which are present in trace amounts in the stones. Their resistance to breakage is generally regarded as poor because of their high level of inclusions. The word “emerald” is derived from the Latin word “smaragdus,” meaning green.
Emeralds are found in a wide variety of hues, anything from yellowish green to bluish green. Yellow and blue are the secondary hues found in emeralds. The primary hue is always green. Only the gems that are medium to dark in tone are emeralds. If they are lighter in tone, they are considered green beryl. The hue is always vivid with a gray mask, or saturation modifier. A very fine emerald will have a vivid green hue, with the secondary blue or yellow hue only slightly modifying the stone and no gray mask visible.
Emerald clarity is graded by sight because of its many surface fissures and inclusions. If it has no flaws that are visible to the naked eye, it is considered perfect. Emeralds that do not have fissures and breaks are extremely rare, and so all are typically treated to enhance clarity.
Emeralds are treated to improve surface clarity with a process known as oiling. Cedar oil is most commonly used for the oiling. However, other oils may also be used as long as they have a similar refractive index. The U.S. Federal Trade Commission requires that the treatment be disclosed to the consumer upon purchase of an emerald. Consumers should always request a treatment report before buying, as two emeralds that appear to be of the same quality may be far apart in their level of treatment.
Emeralds were once found in Austria, Pakistan and Egypt. Today, the most valuable emeralds are mined in Colombia and are prized for their natural fire and transparency. Some of the rarest emeralds come from mines in Colombia. Other countries that produce the gemstones include Russia, Afghanistan, Zambia, Zimbabwe, Brazil, India and Madagascar. Emeralds can also be found in North Carolina in the United States.
Emeralds are popularly known as the birthstone of May. They are also recognized as the birthstone of the zodiacal signs of Taurus, Cancer and Gemini, although this depends on the astrological tradition. In some cultures, emeralds are considered traditional gifts for the 20th, 35th and 55th wedding anniversaries. The King James Version of the Bible lists emerald as one of the gemstones embedded in the breastplate of the Jewish high priest.