Hong Kong - A 101-carat colourless diamond the size of a squash ball sold for a record 46.2 million US dollars at a Christie's auction in Hong Kong, a radio report said Thursday.

The gem, the biggest colourless diamond ever sold in Asia and one of only three colourless diamonds over 100 carats ever sold, was bought by a private buyer at the Christie's auction in Hong Kong Wednesday.

Government-run radio station RTHK said Thursday the buyer's identity was not being revealed but he would have the option to name the diamond, the most expensive single piece of jewelry sold in Asia.

The diamond, which is set in a tiara, was the biggest colourless diamond to come up for auction anywhere in the world for 18 years, according to Christie's.

Diamond prices have boomed in recent years partly because of the economic slowdown, with new buyers from Russia, India and Asia pushing auction prices higher. (dpa)