World's most expensive diamond to be auctioned

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Pink Star

The Pink Star diamond is going under the hammer in Geneva this November, when it is expected to become the most expensive diamond ever to be auctioned. Sotheby's estimates that a willing buyer will pay an incredible £40 million for the stone.

So why is it worth so much?

The diamond

The oval diamond was mined in 1999, and cut and polished for two years. It was unveiled in Monaco in 2003 and sold in 2007 - when it was named 'The Pink Star'. There are several reasons why the auction house has placed this massive valuation on the stone.

First it's pink - which is rare in itself - and is the most highly prized of all coloured diamonds. Second it is flawless, which is also rare. And third, it is absolutely enormous. It's a stunning 59.6 carats. They say it's the largest internally flawless fancy vivid pink diamond that the Gemological Institute of America has ever examined.

David Bennett, Chairman of Sotheby's Jewellery Division in Europe and the Middle East and Chairman of Sotheby's Switzerland, said that the rarity, quality and size: "surpass those of any vivid pink diamond in State, Royal or private collections." He added: "It is difficult to exaggerate the rarity of vivid pink diamonds weighing only five carats, so this 59.6 carat stone is simply off any scale."

Most expensive

There is certainly a precedent for pink diamonds fetching incredible prices. The most expensive pink diamond ever sold (measured per carat) was a 5 carat diamond ring by Graff, which sold for $10.8 million in 2009. The Pink Star is clearly a far larger stone, so the price will reflect that.

The world record for the most expensive pink diamond ever sold at auction was the much larger Graff Pink, a 24.78 carat rectangular diamond sold by Sotheby's Geneva in 2010. It fetched $46.2 million. Given that The Pink Star is so much larger, there's an argument that it could smash this record when it is auctioned in November.

Investment

For the buyer that's no knowing whether it will turn out to be a good investment. Diamond traders say that for the last five years the price of diamonds between one and five carats has risen 12% a year, and that they could rise 10% this year. However, it's in their interests to drum up trade, so you need to be careful about taking these figures at face value.

Anyone investing in diamonds has to face the fact that valuing them is difficult and that even the experts often disagree about what a diamond is worth. Selling them is also less-than-straightforward, and if you sell them at auction you will only get what the highest bidder is prepared to pay on the day. Of course, with a diamond as rare as The Pink Star, you can be sure that the price on any given day is likely to be eye-watering.