The largest flawless diamond ever to be auctioned is set to go under the hammer in May at Christie's in Geneva. It is expected to sell for a small fortune, because perfect diamonds like this are incredibly rare - and ones of this size are almost unheard of.
So what will it fetch, and how does it compare with the most expensive diamonds ever sold?
The diamondThe pear-shaped diamond weighs an incredible 101.73 carats. It was carved from a 236-carat rough diamond found in Botswana, which took 21 months to polish. However, it's not just the size of the diamond that makes it so rare - it's of exceptional quality too.
It meets every criteria of perfection, and has been graded by the Gemological Institute of America with the best colour, D, and the best clarity, Flawless. It is also unusually brilliant, because of a rare chemical make-up.
The combination of size and quality means it is one of a handful of gems of this type. Plus, the person who buys it gets to name it, which will offer them a place in gem history.
How does it compare?It goes down as one of the finest diamonds Christie's has ever sold. The current auction record for a colourless diamond was set by the historical 76.02 carats cushion-shaped Archduke Joseph Diamond when it sold for US$21.5 million at Christie's Geneva in November 2012. This one had a bit more history on its side - but was smaller and of lower grade.
It is likely to be one of the largest flawless diamonds ever to come to auction, as exceptional gems tend to be reserved for royalty. The world's most famous pear-shaped diamond is the Cullinan I, a colourless 530.20 carat diamond, which forms part of the Crown Jewels. This is also the largest colourless diamond known.
However, size and quality are only part of the story. In December 2011, Christie's New York sold a 33.19 carat Elizabeth Taylor Diamond ring that the star wore virtually every day since receiving it as a gift from Richard Burton in 1968. This was far smaller, and yet fetched $8.8 million.
Christies told AOL that it expected to sell the gem for more than $20 million.