Rare 'Martian Pink' diamond sells for more than double estimate

The 'Martian Pink' was sold at an auction in Hong Kong with a winning bid of US $17.3 million (£11 million), it had been expected to reach around US $7 million.

At 12 carats, the diamond is a little smaller than a five-pence piece.

The stone gets its name from the American jeweller Ronald Winston who gave it the name in 1976 to mark the US sending a satellite to the Planet Mars.

Coloured diamonds - known as "fancy" diamonds in the industry - are extremely rare. The most common colours are black, blue, brown, yellow ("canary") and pink.

Blue and pink diamonds are considered to be the most rare and most jewellers will never see one in their careers.

Queen Elizabeth II owns one of the most famous pink diamonds. The Williamson Pink was a gift on her wedding in 1947. The 23.6-carat gem is now set in a brooch in the design of a five-petalled flower.

The Queen wore the brooch when she hosted the US President Barack Obama and his wife Michelle at Buckingham Palace in April 2009.

The largest pink diamond in the world is the Darya-ye Noor, meaning "Ocean of Light" in Persian. At 182 carats, it is one of the largest diamonds in the world. It forms part of the Iranian Crown Jewels.

The auctioneer Christie's says the Martian Pink is the largest round intense pink diamond ever to be auctioned.