According to auction house Sotheby's, a rare, flawless 'Blue Moon' diamond set a world record for gemstone auctions, selling for $48.4 million on Wednesday. Hong Kong tycoon Joseph Lau, who bought a pink diamond a day earlier, bought it and renamed it 'The Blue Moon of Josephine' after his daughter. This diamond beat the 24.78 carat, $46.2 million 'Graff Pink'.