£48m! Pink diamond at a price to make you blush . . .

It’s pink, perfect – and very, very pricey. One of the world’s great natural treasures, this 59.6-carat diamond is expected to fetch £48million at auction – making it the largest and most expensive cut gem in history.

the stone, known as the Pink star, was unveiled in London yesterday ahead of its sale in Hong Kong next month. It is more than twice the size of the 25-carat Graff Pink – which holds the pink diamond auction record at £37.3million.

It is also expected to out-price the famous Oppenheimer Blue, which became the world’s most valuable diamond when it fetched £40million last year. Coloured gemstones are highly prized. Kate Middleton’s engagement ring carries a 12-carat blue Ceylon sapphire and singer Jennifer Lopez wore a 6.1-carat pale pink diamond during her ill-fated relationship with Ben Affleck.

Pink diamonds, the rarest of all, are known for their unique levels of purity and ‘extraordinary optical transparency’.

the oval mixed-cut Pink star is the largest internally flawless fancy vivid pink diamond ever graded by the Gemological Institute of America. Experts have called it ‘perfect in every way’ and say it could even sell for as much as £80.8million on the back of a boom in the international economy.

David Bennett of auction house sotheby’s said the size and colour of the gem makes it the most impressive pink diamond ever known. He said: ‘the extraordinary size of this 59.6-carat diamond, paired with its richness of colour, surpasses any known pink diamond recorded in history.’

the Pink star was originally a 132.5-carat rough diamond when it was mined in south Africa in 1999 and underwent two years of meticulous cutting and polishing.

It was offered at auction by sotheby’s in 2013 and fetched £52million, but the American buyer defaulted on the payment.

Despite its size, experts say the diamond can still be fitted into a ring.