THE most valuable cut diamond ever to be offered at auction has gone on display in London.

The Pink Star is expected to sell for more than $60 million (£48.4m). The auction record is currently held by the Oppenheimer Blue, which fetched 50.6 million Swiss francs (£35m) at Christie’s in Geneva, Switzerland, last year.

At 59.60 carats, the Pink Star is more than twice the size of the Graff Pink – the 24.78-carat gem which holds the pink diamond auction record.

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The Pink Star sold for more than $83m (£52m) at an auction in Switzerland in 2013, but is back on the market after the sale defaulted.

David Bennett, Sotheby’s jewellery division’s worldwide chairman, said: “At a time of unprecedented demand for the finest in coloured diamonds, I am delighted to be bringing this magnificent stone back to the market. The extraordinary size of this 59.60-carat diamond, paired with its richness of colour, surpasses any known pink diamond recorded in history.”

The diamond is on display at Sotheby’s London offices before its sale on April 4 in Hong Kong.

Mined by De Beers in Africa in 1999, the 132.5-carat rough diamond was cut and polished over a period of two years. The Cullinan Diamond is the largest gem-quality rough diamond ever found. weighing 3,106.75 carats (621.35 g), and was discovered at the Premier No. 2 mine in Cullinan, South Africa, on 26 January 1905. It was named after the chairman of the mine, Thomas Cullinan.

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It was split into nine separate diamonds and some are part of the British Crown jewels.

Sotheby’s says demand for investment-grade diamonds remains strong, especially for the best, rarest stones.