Sotheby’s has been able to sell a 72-carat flawless diamond privately, when it could not sell it at the Hong Kong jewellery auction. The reason was a confusion over the foreign-exchange conversion for the gem, reports Bloomberg. The stone is graded as a D-colour pear-shaped diamond. %% It commanded a presale value of HK$100 million ($12.8 million). The final bid it received at the auction was HK$73 million ($9.3 million). Although the stone attracted bids form buyers all over the world, the amount could not match upto its reserve price. The company has not divulged the details of the sale to the private party.