A rare pink diamond has fetched 50.3m Swiss francs ($50m; £38.5m) at auction, a record price per carat.

Pink Legacy, weighing in at just under 19 carats, was bought by US brand Harry Winston at auction in the Swiss city of Geneva.

The rectangular-cut stone was found in a South African mine around 100 years ago and has likely not been altered since it was first cut in 1920, the auction house Christie’s said.

Finding a fancy vivid pink diamond larger than 10 carats is virtually unheard of, the auction house said.

The price of around $2.6m per carat marked a world record for a pink diamond, according to the Europe head of Christie’s.

It had been valued at between $30-$50m before sale, and was bought after only five minutes of bidding.

The diamond’s new owners have rechristened it the Winston Pink Legacy.