FAMOUS DIAMONDS 'DRESDEN GREEN'.
In the rough, greenish diamonds tend to occur as one of three types: a stone, often a crystal, possessing a light tinge rather like the colour of water in a swimming pool; a stone with a dark green skin not dissimilar to the colour of a well-known brand of gin bottle; a yellowish-green stone characterized by a degree of lubricity. After they have been cut and polished, diamonds of the first and second types usually lose their greenish tinge to become fine blue-white gems or, alternatively become yellower, as silvery capes. The few green polished diamonds, therefore, originate from the third type. The famous collection of De Beers 'fancies', which has been displayed in many places through out the world, includes some beautiful examples.
Since this is an account of a truly unique gem, a scientific explanation for the phenomenon of green diamonds is called for. The green colour is usually caused by the crystal's coming in contact with a radioactive source at some moment during its lifetime and in geological times. This is measured in millions of years. The most common form of irradiation encountered by diamonds is by the alpha particles which are present in the magma or kimberlite in minute quantities. Long exposure to these particles forms a green spot on the surface of the diamond, or sometimes produces a thin green coating which is only skin deep and can easily be removed by polishing the stone on a scaife. But bombardment by beta and gamma rays as well a neutrons will discolour the stone to a greater depth and in some cases turn the whole of the stone's interior green.
Heating the stone may sometimes improve its colour but care must be taken to keep the below 600oC, because at this critical temperature the green colour is liable to turn to a light yellow or brown. The change in colour is due to the change in the crystal's lattice structure. Before bombardment by redioactive particles the crystal's lattice was stable but the initial radioactive shock was sufficient to disturb the equilibrium and produce a green discolouration. Annealing will distort the lattice further and produce another change of colour. This phenomenon is similar to a piece of elastic that has been overstretched at some time; it will come back so far, but never returns to its original length. Similarly, after treatment the diamond's lattice remains permanently distorted.
Research has disclosed that green or irradiated diamonds are common in all areas where diamonds are mined: Africa, India, the USSR, or South America. But green stones of any size are rare; in this respect the 'Dresden Green' which probably weighed over 100 old carats in the rough, is unique among the world's famous gems. The gem is of an apple-green colour and superb quality. It is cut as a pendelopue, with 58 facets, and weighs 40.7 metric carats.
Unlike some other famous diamonds, the 'Dresden Green' has led a comparatively untroubled existence. It derives its name from the Saxon capital where it has been on display for more than two hundred years. In 1742, Frederick Augustus II the Elector of Saxony, purchased the gem from a Dutch merchant at the Leipzig Fair for £30,000. However, it was this ruler's father, Frederick Augustus I, known as Augustus the Strong, who transformed Dresden in a centre of intellectual and artistic activity as well as a marvel of 'baroque architecture'. He was a man of luxurious and extravagant tastes who sought to model his court upon that of Louis XIV at Versailles.
Frederick Augustus I was responsible for the erection of some outstanding buildings in Dresden which he duly filled with great collections of rare and costly treasures. He amassed a collection of Crown Jewels as the ruler of Saxony, and when he was elected to the throne of Poland in 1697 he commanded new regalia to be made for his coronation. A collection of Jewels was housed in Dresden Castle..
The contents of the Green Vault remained on display to the public until the beginning of the Second World War. However in 1958 the Soviet government returned the Saxon treasures to Dresden and the green diamond is now on display again in its former home.
There is one more point of interest about this wonderful diamond. It has always been stated that it is of Indian or East Indian origin. Yet if it had been mined in the East it is perhaps a little surprising that nothing appears to have been known in Europe about such a stone until the middle of the eighteenth century. Is there a distinct possibility the 'Dresden Green' may have come from Brazil!
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