Emerald

History
As with most rare jewels, royalty and people of status readily adorned themselves with these sparkling green gems. The Roman emperor Julius Caesar collected emeralds on the grounds that they had healing powers. He even had his portrait carved into a 225-carat emerald. Leaders such as Charlemagne wore crowns studded with emeralds. At his coronation in 1171 Henry II, King of the Irish, was given an emerald ring to symbolise his power. The most striking emerald collection of all time, however, is contained in the crown of the Holy Virgin Mary, Queen of the Andes. The crown was created by the people of Popayán, a Colombian town, in gratitude for their survival of a three-year plague. This masterpiece was created over six years from one single gold nugget and adorned with 453 emeralds weighing a total of 1521 carats.

 

Colour
The description of an emerald’s colour rarely does its beauty adequate justice. The vegetative greens of Mother Nature vary depending on the seasons, the weather and the crispness of the air; the greens of the emerald are just as multifaceted. The palette of shades is delicate and subtle and ranges from pale leaf green through to a dark fir green. Dr. Eduard Gubelin described the most precious green colour as a dewy green of fresh spring grass, intense and clear.

 

Gemmological Properties
The emerald is a member of the beryl family, its chemical composition being beryllium aluminium silicate. The unique green of this gem is due to traces of chromium oxide found throughout the mineral. Each chromium oxide atom replaces one aluminium atom, a phenomenon that distinguishes the emerald from a beryl. The higher the number of chromium atoms, the more intense the green. However, the reduced amount of alumina causes the silicate rings to weaken, a factor that increases the brittleness of the emerald: the gemstone is more sensitive and fragile than others of the same hardness.

 

Even during its growth, the emerald is very sensitive and exposed to all manner of inner tensions. Fissures are easily formed, leaving the gem susceptible to fractures if not looked after carefully.

 

Mining Areas
Until the late Middle Ages there were only two known emerald deposits: Jebel Sikai in Egypt and the Habach Valley in Austria. It was only when the Spanish landed in South America in the 16th century that further deposits were discovered. Initially these “deposits” were, sad to say, the palaces and temples of the Aztecs and Incas. These civilisations tried desperately to keep secret the whereabouts of their source, and it was only by chance that the Muzo mine in Colombia was finally discovered. Even today this mine remains the source of the most exquisite emeralds.

 

Beryllium and chromium, essential for the creation of an emerald, are rarely encountered together in nature, hence the rareness of fine emeralds. The best quality emeralds, still now, come from the Muzo and Chivor mines in Colombia. In more recent times, other gem-quality deposits have been discovered in countries such as Afghanistan, Pakistan, Brazil, Zimbabwe, Russia, Australia and India.

 

Old Mine, Old Indian Mine emeralds: Myth or Reality
The term “old mine” are used in the trade to describe emeralds which are considered antique, typically of considerable size, and cut in an antique manner, often carved. As Indian Maharadjahs and Emperors of the Mughal dynasty adorned themselves with such stones, old mine emeralds are considered valuable not only for their beauty and quality, but also for their pedigree. The term “old Indian mine” is sometimes used for the same type of stones, however, it has no relation to the Indian subcontinent, according to the findings of the research conducted by Professor Gaston Giuliani from the University of Nantes. By means of oxygen isotope analysis, he showed that all antique stones with a traceable history are coming from the Colombian mines of Muzo, Cosquez and La Pita. No evidence was found for the alleged Indian or Afghani-Pakistani origin. This is consistent with the experience gathered by the Gübelin Gem Lab over many decades: emeralds supplied to us as Old Mine stones – many of them of superb beauty and quality – were found to be of Colombian origin. Old Mine emeralds are thought to be brought to Europe by the Spanish, and further to the trade routes to Asia. Unless the pedigree is properly documented, antique emeralds from the Mughal era cannot be differentiated by analytical means from recently found emeralds cut and carved in an antique style. Thus, the term “old mine” or “old Indian mine” should not be used by gem labs to indicate a geographic origin or a mining period.