12.00ct. Emerald and diamond ring.
Emerald, the birthstone for May, is a symbol of rebirth, appropriate for spring. Emerald was thought to bring the wearer foresight, good fortune and youthfulness. The Romans believed that emerald represented fertility. The gem is also thought to represent wisdom, growth and patience, and when given as a gift it represents love and fidelity. The emerald duplicates lush landscapes and the richest of greens, and has been coveted for centuries. Emerald was first mined in Egypt. Today, emerald is mined in Colombia, Brazil, Zambia and Afghanistan.
The Egyptians mined emeralds as early as 1500 BCE. The earliest known mine is at Gebel Zabara, along the upper Nile River. Egypt was the major source of emerald until the sixteenth century, when Spanish conquistadors saw the abundance of emeralds of the Incas. In 1537, the conquistadors took over the mines in Chivor and Muzo in Colombia after defeating the native populations. The Muzo mine has been active since the 16th century, producing some of the finest emerald.
The emerald belongs to the beryl family. This group also includes aquamarine, as well as an array of other color gemstones. The most desired emeralds are bluish green to green, with a strong to vivid saturation and have a medium to medium-dark tone. The color should be evenly distributed with no color zoning. If the color falls outside of the bluish-green to green range, it is no longer deemed an emerald, but a variety of beryl. Aluminum, silicon, oxygen and beryllium are the elements that an emerald contains. The trace elements that create the beautiful green color are chromium, vanadium and iron. Most emeralds are found in regions with metamorphic rock.
The emerald cut shape is the most common for emeralds due to the crystal structure. The shape of the crystal accommodates the emerald cut shape with minimal weight loss. If the crystal is heavily included, the cutter will create a cabochon. Cutting emeralds is more difficult than sapphires or diamonds. Emeralds have factures, which make them brittle and vulnerable to damage in the cutting, polishing and setting processes. They are more fragile than diamond and sapphire and are easily damaged while wearing in jewelry.
Most emeralds have inclusions that are visible to the unaided eye. Eye clean emeralds are extremely rare and valuable. Emeralds are classified as being slightly, moderately, or heavily included. Generally emeralds with a higher transparency, clarity and some inclusions, are acceptable for valuable emeralds.
Ninety percent of emeralds are treated. The most popular treatment is soaking the stones in oils. These oils have close to the same refractive index of emeralds and seem to lessen the appearance of the fractures. Many different oils are used to fill the fractures such as cedarwood, castor, coconut, corn, linseed, or mineral. Filling the fractures can improve the color by making it look deeper and more even. Oiling an emerald is not a permanent treatment. Over time oils can evaporate or leave a residue. Another treatment is with resins, which are more durable than oil. The first type to be used was the resin from the balsam fir. Now, manmade resins such as Opticon, Gematrat or Permasafe, are used. These minor treatments do not detract from the beauty or value of an emerald.
Emerald Crystal from Muzo mine.