These fascinating gemstones are a member of the Beryl family, which includes blue aquamarine and pink morganite. Pure Beryl is colourless, but traces of chromium and vanadium in the Beryl produces the green colour of emeralds.
|Emerald Crystals. Photo © globe-views.com|
Only Beryl gems that are medium to dark green in tone are considered emerald, with the most prized stones being transparent and a vivid green with lots of depth. During the 1960s, the American jewellery industry redefined emeralds to include beryls with vanadium inclusions (confusingly often referred to as "Colombian Emeralds"), but these are not recognised as true emeralds in the UK or Europe.
Like other members of the Beryl family, emeralds feature large and perfect six sided crystals. But unlike other Beryls, which are hard and durable stones, emeralds are brittle and their resistance to breakage is poor. They also have a tendency to crack if subjected to extreme temperature fluctuations.
|Emerald Crystals. Photo © fieldgemology.org|
Unlike diamonds, emeralds are graded by eye. An emerald with no visible inclusions would be considered flawless - but it is extremely rare to find an emerald like this! Most emeralds contain inclusions and a cloudiness - known as jardin - that can be seen by the naked eye. Interestingly, it is the presence of these flaws that tell an expert where the emerald originated.
Because of the presence of flaws, emeralds are a difficult gemstone to cut - so much so that the bevelled edge "emerald cut" was specially developed. For centuries, emeralds have been oiled to improve their clarity, and some stones are dyed to improve their colour. As a result, emeralds should never be washed with soap or in an ultrasonic jewellery cleaner as this can remove the oil and reveal hidden flaws in the stone.
|An "Emerald Cut" Emerald. Photo © Gemfields Mine, Zambia|
Nowadays the best emeralds nowadays are mined in Colombia, Brazil and Zambia, before being sent to the emerald capital of the world, Jaipur, for cutting and polishing. But emeralds have a long history. They were first mined at least 4,000 years ago in Egypt, although "Cleopatra's Mines" had been exhausted long before they were rediscovered in the 19th century.
The Incas regarded the emerald as a holy gemstone, while the Mughal Emperors associated it with paradise (emerald green is the official colour of Islam). One of the largest emeralds ever found is the "Mogul Emerald", which was mined in Colombia and weighs a massive 217.80 carats. It was carved in around 1695, with a Shi'ite prayer on the front and a flower and leav design on the back. In 2001, this amazing emerald was sold by Christies in London for over $2million USD.
|The Mogul Emerald © Christies.com|