(IDEX Online) - The largest purple-pink diamond ever to go under the hammer could fetch as much as $38m.The "fancy vivid purple-pink internally flawless" 15.81-carat type IIa IF diamond (pictured) is the highlight of a Christie's Hong Kong live auction in May. It has a strong pink hue with a secondary color of purple and has been named the Sakura Diamond because it perfectly matches the petals of the Sakura cherry blossom."As fewer than 10 per cent of pink diamonds weigh more than one-fifth of a carat, this fancy vivid purple-pink diamond is of an unprecedented size of 15.81 carats, which is the largest of its kind (fancy vivid purple-pink) to be offered at any auction," said the auction house.The gem carries an estimate of $25m to $38m. Only four per cent of pink diamonds have a color deep enough to qualify as 'fancy vivid'. The Hong Kong Magnificent Jewels Live Auction takes place on 23 May.