Emerald

Emerald is the most precious stone in the beryl group. The name emerald comes from the Greek "smaragdos" via the Old French "esmeralde", and really just means 'green gemstone.' The wonderful green color of emerald is unparalleled in the gem world. It is not surprising then that emerald is classified as one of the traditional four precious stones along with sapphire, ruby and diamond. Emerald is the birthstone for May and for commemorating the 20th and 35th wedding anniversaries. Emerald's precious green color is caused by trace amounts of chromium and vanadium. Almost all natural emeralds contain characteristic inclusions. For that reason emeralds are generally more fragile than other beryls and must be handled more gently. Almost all emeralds are treated with oil or resins to fill tiny cracks. With emerald, even more than other colored gems, it is color which is the chief determinant of value.

Emerald, by definition, is a medium or darker green to blue green beryl, in which the green color is derived from impurities of chromium, vanadium, or a combination of both. The most popular and valuable color is a slightly bluish green in a medium dark tone with strong to vivid saturation. The term "Colombian" emerald is often been used to describe vivid, slightly bluish green stones of medium, to medium dark color, no matter what their actual geographic origin. Emeralds of lighter color are sometimes called "Brazilian" emerald, even if they were mined in Africa.  Emerald looks best in daylight. Artificial light will expose inclusions and fractures that prove the stone to be a natural emerald.

Clarity is important, but inclusions are tolerated more in emerald than virtually any other gem. Unlike other beryl gems, emeralds often contain inclusions and other flaws. These flaws are not looked on as negative aspects for emerald like they would be for other gemstones. Indeed, these flaws are considered part of the character of the stone and are used to assure the purchaser of a natural stone.

Cutters love this unique gem. Indeed, they have developed a special cut just for this gem: the emerald cut. The clear design of this rectangular or square cut with its oblique corners brings out the beauty of this valuable gemstone to the full, at the same time protecting it from mechanical strain. Emeralds are also cut in many other, mainly classical shapes, but if the raw material contains a large number of inclusions, it may often be cut into a gently rounded cabochon, or into one of the emerald beads, which are so popular in India. Clear, transparent specimens come sometimes as brilliant cuts. Emerald mining is nearly exclusively from host rocks, where the emerald has grown into small veins or on walls of cavities.

Colombia is the world center of mining emerald. The Muzo mine, northwest of Bogotá, produces fine-quality stones of a deep green color. The Chivor mine, northeast of Bogotá, is another important deposit, other locations promise additional successful mining results. Brazil has various deposits in Bahia, Goias and Minas Gerais. The stones are lighter than the Colombian ones, mostly yellow-green and are often free of inclusions. Brazil also supplies rare emerald cat's eyes and extremely rare emeralds with a six-ray star. South Africa deposits concentrate in the northern Transvaal. But only five percent of the stones found in the Cobra and Somerset Mines are of good quality. Most stones are light or muddy and only suitable for cabochon cuts.

Zimbabwe has several deposits of emerald; the most important is the Sandawana mine in the south. The crystals are small, but of very good quality. Russia has deposits in the Ural north of Sverdlovsk. Good qualities are rare; most stones are light or muddy and only suitable for cabochons.  Further deposits are in Afghanistan, Australia (New
South Wales, Western Australia), Ghana, India, Madagascar, Malawi, Mozambique, Namibia, Nigeria, Pakistan, Tanzania, Zambia and the United States (North Carolina).

Oiling is a common treatment of emerald. This term refers to the practice of immersing emeralds in a colorless oil or resin. Often this is done using a vacuum chamber to assist penetration. Non-standard treatments go beyond this to using green colored oils and hardened, epoxy-like resins. These treatments dramatically improve the appearance of the gems, but necessitate special care in cleaning and setting. Steam cleaners, solvents and ultrasonic can remove the oils, making inclusions that had barely been visible stand out in sharp relief. That damage is temporary only, since emeralds can be re-oiled.

One of the world's largest is the so-called 'Mogul Emerald'. It dates from 1695, weighs 217.80 carats, and is some 10cm tall. One side of it is inscribed with prayer texts, and engraved on the other there are magnificent floral ornaments. This legendary emerald was auctioned by Christie's of London to an unidentified buyer for 2.2 million dollars on September 28th 2001. Emeralds have been held in high esteem since ancient times. For that reason, some of the most famous emeralds are to be seen in museums and collections. The New York Museum of Natural History, for example, has an exhibit in which a cup made of pure emerald, which belonged to the Emperor Jahangir, is shown next to the 'Patricia', one of the largest Colombian emerald crystals, which weighs 632 carats. The collection of the Bank of Bogotá includes five valuable emerald crystals with weights of between 220 and 1796 carats. Splendid emeralds form part of the Iranian National Treasury, adorning, for example, the diadem of the former Empress Farah. The Turkish sultans also loved emeralds. In Istanbul's Topkapi Palace there are exhibits with items of jewelry, writing-implements and daggers, each lavishly adorned with emeralds and other gems. The Viennese treasury contents a vase, 4.5 inches (12 cm) high, with a weight of 2205ct, which is cut from a single emerald crystal.  Her majesty, Queen Elizabeth II, has so much jewelry that she has a special room to keep it in, said to be about the size of an ice rink, and situated 40 feet beneath Buckingham Palace. That does not even include the British Crown Jewels, which are kept in the Tower of London. The Queen's personal jewelry is conservatively valued at $57 million and most of it was received as gifts. The fabulous gems in her collection include the "Cambridge and Delhi Dunbar Parure", a fantastic suite of emerald jewelry which includes an emerald diadem.

Emerald Gemology
Species: Beryl
Color: Emerald green, green, slightly yellowish green
Chemical composition: Al2Be3Si6O18, aluminum beryllium silicate
Crystal system: (Hexagonal), hexagonal prisms
Hardness: 7.5-8 (Mohs scale)
Specific gravity: 2.67 - 2.78
Refractive index: 1.565 - 1.602
Birefringence: -0.006
Absorption spectrum: 683, 681, 662, 646, 637, 606, 594, 630-580, 477, 472
Fluorescence: Usually none

Innumerable fantastic stories have grown up around this magnificent gem. The Incas and Aztecs of South America, where the best emeralds are still found today, regarded the emerald as a holy gemstone. However, probably the oldest known finds were once made near the Red Sea in Egypt. These gemstone mines, already exploited by Egyptian pharaohs between 3000 and 1500 B.C. and later referred to as 'Cleopatra's Mines', had already been exhausted by the time they were rediscovered in the early 19th century. Written many centuries ago, the Vedas, the holy scriptures of the Indians, say of the precious green gems and their healing properties: 'Emeralds promise good luck' and 'The emerald enhances the well-being'. So it is no wonder that the treasure chests of Indian maharajas and maharanis contained wonderful emeralds.

Emerald is the birthstone for those who are born in May. Emerald is the gemstone for commemorating the 20th and 35th wedding anniversaries.