The Queen's personal jewels made from the world’s largest diamond go on display

Exhibition curator Caroline de Guitaut holds the Cullinan III and IV Brooch. Photographer: Ian Jones
Wednesday, 16 May 2012

Brooches, a ring and a necklace made from the largest diamond ever found go on display at Buckingham Palace this summer. The special exhibition Diamonds: A Jubilee Celebration reunites for the first time seven of the nine principal stones cut from the Cullinan Diamond that now form part of Her Majesty The Queen’s personal jewels.

The Cullinan Diamond, which weighed 3,106 carats in its rough state, was discovered at the Premier Mine near Pretoria in South Africa in 1905.  At first the stone was assumed to be a crystal, as it is three times larger than any other diamond that has been discovered.  When it was taken to the mine manager’s office, the clerks threw it out the window, unable to believe that something so big was a diamond.  Eventually they were persuaded, and the diamond was named after the chairman of the mining company, Thomas Cullinan.

Measuring 10.1 x 6.35 x 5.9cm, the diamond was notable for its extraordinary blue-white colour and exceptional purity.  Although it is the largest stone to have ever been found, the rough diamond had a cleavage face on one side, which suggested that it might once have formed part of an even larger stone.  Soon after being discovered, it was sent to London and taken to Buckingham Palace for inspection by King Edward VII.  For the next two years the stone remained a public wonder, during which time it was shown to many prospective clients – although it was hard to find a buyer, as no one could understand how a stone so big could possibly be cut.  Eventually the Prime Minister of the Transvaal suggested that his government should acquire the Cullinan and present it to Edward VII as a token of loyalty.

The gift did not include the cost of cutting the stone, and this task was entrusted to the celebrated firm of IJ Asscher of Amsterdam.  No one had ever cut such a huge stone – and the complexities of doing so were many.  It was too large to be cut into a single gem, so cleaving or sawing was necessary.  After weeks of consideration, including four days spent making the groove into which the steel cleaving knife was to be inserted, the stone was ready to be split.  The first blow broke the knife, but the diamond remained intact.  A second cleavage knife was fitted, and this time the blow split the diamond in two.  A few days later, the task of dividing up these two large pieces began.  Eight months of grinding and polishing followed, for three polishers working 14 hours a day.  Eventually, they produced nine principal numbered stones, 96 small brilliants and nine carats of unpolished fragments. The total weight of the gems cut from the Cullinan amounted to 1,055.9 carats.

Exhibition curator Caroline de Guitaut said, ‘Until 26 January 1905 no one had ever seen a diamond of this size. So incredible was its discovery that the moment it was found at the Premier Mine it was thrown out of the window of the mine manager’s office because it was thought to be a worthless crystal.  Now, for the first time, our visitors will be able to see seven of the nine principal stones cut from this magnificent and highly important diamond.’

Buckingham Palace is open 30 June - 8 July and 31 July - 7 October 2012.