About Colombian Emeralds
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ABOUT COLOMBIAN EMERALDS: VIVA LA VERDE
PHYSICAL CHARACTERISTICS: CUTS, SHAPES, SIZES
Emeralds belong to the mineral group of silicates and are classified as Beryl. Their chemical composition is Al2Be3 (Si6O18) and have a hardness is 7-1/2 – 8 on the Moh’s scale. Specific Gravity ranges from 2.67-2.78 and a refractive index from1.576-1.582. The finest quality Colombian Emeralds are almost universally fashioned in the trap-cut style which has truncated corners giving and elongated octagonal outline. This style, due to its common association with emeralds has now been come to known as the octagon shape with emerald cut.
This cut has few plane facets and this shows the saturated deep velvety green of emeralds to best advantage. Inferior to the finest gem-quality Colombian emeralds are cut en round, cushion, princess, cabochon or beads. You may also find Colombian emeralds to be carved especially if the material exhibits good to strong color though it can have many fissures and flaws.
The emerald mines of Colombia are located in the Cordillera Oriental which is the eastern range of the Andes. They lie to northeast of Bogota, the capital of Colombia in the departments of Boyaca, Cundinamarca, and Santander. Colombian emeralds are mined from two zones: the western zone that includes the Penas Blancas, Cosquez, Muzo and Yacopi mining regions and the eastern zone that includes the Chivos/Somondoco and Gachala mining regions.
The yellowish green stones from the Muzo district have a warm velvety appearance that is most prized. While best-quality Muzo emeralds tend to have a well-saturated slightly yellowish-green color, Chivor emeralds tend to have a slightly less saturated bluish-green color. Cosquez emeralds occur in a wide range of colors and clarities but in best qualities they have a dark slightly bluish-green color. Emerald crystals from the Chivor mines are usually of a good blue-green color but are often shattered due to the force of earlier geological events.
Emeralds from most origins are commonly treated in the market today. A very widespread and internationally accepted practice in the wholesale trade of emeralds is to treat them with some form of fine oil in order to disguise the very frequent appearance of flaws, such as fractures and cavities. However responsible dealers in Colombia who deal extensively in emeralds employ oiling methods only with the agreement of their clients and practice great care and skill in carrying out the process. It is believed that the oil preferred for treating Colombian emeralds is cedar oil that has a refractive index close to that of emerald. The polished emeralds are first placed in small beakers containing hydrochloric acid in a vacuum chamber for a considerable time, the acid is removed from the stones and they are subjected to an ultrasonic treatment to remove any oxide left over. Then the stones are immersed in slightly warm cedar oil and left at a certain temperature for a long time. Recently commercial epoxy plastics like Opticon or a treatment like the Yehuda glass treatment are also used to treat emeralds, however at Beacab Gems we do not buy or sell such emeralds.
Emeralds that earn the “No Oil” or “Insignificant” with a “Traditional – Oil” treatment mark are extremely rare to find in the gem industry and command extremely high premiums. Collectors and Consumers can expect to pay as much as $100,000 per carat for such earthly treasures.
The 37.82-carat Chalk Emerald set in a ring has great clarity and its deep green color is often counted among that of the very finest Colombian emeralds. Legend has it that it was once the centerpiece of an emerald and diamond necklace belonging to a maharani of the former state of Baroda in India. Originally weighing 38.40 carats, Harry Winston Inc re-cut it and set it in a ring along with sixty pear-shaped diamonds totaling 15 carats. The ring was gifted to the Smithsonian Institute by Mr. and Mrs. O. Roy Chalk in 1972 and has remained there ever since. The Guinness Emerald Crystal, found at the Coscuez mines in Colombia and is said to be one of the largest gem quality emerald crystals in the world weighing in at 1759 carats. Although it is part of the collection of the Banco Nazionale de la Republica in Bogotà, Colombia, not much is known about the stone. It has also been reported that five unnamed large emerald crystals from the mines at Muzo have also been acquired and preserved by the Banco de la Republica and these weigh between 1,100 carats and 1,796 carats each.
The 632-carat natural uncut emerald—Patricia Emerald Crystal was named after the mine owner's daughter. It was discovered in the Chivor Mine in 1920 is one of the largest gem quality emeralds in the world. Dihexagonal, or 12-sided, in shape the stone rests in the New York Museum of Natural History at present.
The Hooker Emerald is another famous emerald that is said to have been mined at an unidentified location in Colombia in the 16th or 17th century. Spanish conquistadors sent the rough emerald to Europe where it was cut and polished, before being sold to the ruling family of the Ottoman Empire. The emerald remained part of the crown jewels of the Ottoman Empire until 1908, when many of the Ottoman crown jewels were smuggled on behalf of one of the kings—Abdul Hamid II to Paris. The reason the Sultan did this was because he feared a potential coup by the Young Turks. With the proceeds from the sale of the emerald and other jewels the Sultan hoped to be able to buy a comfortable life in exile should a revolution come to pass. The feared revolution however did take place and the gem dealer —Salomon or Selim Habib auctioned the collection to cover debt repayments.
American jewelry company Tiffany & Co. won the auction and initially set the emerald in a tiara that remained unsold for several decades. In 1950 the stone was removed and re-set into a brooch and in 1955 was purchased by heiress Janet Annenberg Hooker. In 1977, Hooker donated the brooch, then valued at US$500,000, to the Smithsonian Institution in Washington, D.C. where it is on display at a gallery named in Hooker's honor.