The ultra-rare pink diamond, both internally flawless and in the highest color grade category, fetched $17.7 million in Hong Kong at Sotheby's Asia on Tuesday. MediaExpress

The “flawless fancy vivid pink diamond” is so special it needs four adjectives to describe it – and over $17 million to buy it. The pear-shaped, 8.41-carat stone had been expected to fetch $15.5 million, but ended up selling for $17.77 million in Hong Kong, reports Agence France-Presse. The identity of the buyer wasn’t disclosed.

The combination of the pink diamond’s internally flawless clarity, which is extremely rare in pink diamonds, with its “fancy vivid” color grade, a category designating the diamond as having the highest concentration of color, made the stone rare and hence, valuable.

Quek Chin Yeow, deputy chairman of Sotheby’s Asia, said that the diamond "attracted keen competition before fetching a wonderful price of HK$137.88 million (US$17.77 million) and setting a world auction record for a fancy vivid pink diamond." According to the auction house, the flawless fancy vivid pink diamond is “amongst the rarest and most desirable of colored diamonds ever seen at auction.”