The four-day Sotheby's Hong Kong autumn 2007 sale was concluded here on Tuesday, with more than 940 lots sold worth of 1.55 billion Hong Kong dollars (about 200.23 million U.S. dollars).The highlight of the last-day sale was the six-centimeter (2.4- inch) 'Tai Shang Huang Di' White Jade Seal, which was carved in 1796 to mark the abdication of the Emperor Qianlong. It was sold to a Chinese collector for 5.92 million U.S. dollars, a new record for white jade at auction.A Rare Imperial Album comprising the Impressions of Antique Seals from the Collection of the Emperor Qianlong of Qing dynasty was sold at 4.986 million U.S. dollars in Tuesday's auction.On Monday's auction, a flawless blue diamond was sold for 7.98 million U.S. dollars, making it the most expensive gemstone per carat sold at auction. After intense bidding, the 6.04 carat, internally flawless blue diamond fetched 1.32 million U.S. dollars per carat. The price smashed a 20-year-old record held by the Hancock Red - a red diamond which fetched 926,000 U.S. dollars per carat at the time.At Sotheby's Hong Kong Contemporary Chinese Art sale held on Sunday, the total price of sold lots was 42.54 million U.S. dollars, achieving a new world record for the sale of Chinese Contemporary Art.The auction, which saw new artists'records established for Cai Guo-Qiang, Yu Chen, Xu Bing, Liu Wei, Wang Guangyi and Zhan Wang, was highlighted by the sale of The Massacre at Chios by Yue Minjun. After six minutes of intense competition between seven bidders both in the saleroom and on the telephones, the work was finally sold to an Asian private collector for 4,084,202 U.S. dollars, nearly four times of its pre-sale low estimate. The painting is regarded as one of the most important produced during the fledgling years of contemporary Chinese art, and an early example of a piece depicting the artist's characteristic "self-images".Among the three works in the sale by Chinese artist Cai Guo- Qiang, his painting Project for Extraterrestrials No.10, Project to Extend the Great Wall of China achieved a new record for the artist at auction with 2,640,634 U.S. dollars. The painting, which was executed in the unusual medium of gunpowder on paper and is made up of five pieces, is monumental in size measuring approximately 3 by 20 meters, and reflects and records an explosion event in 1993 at Jiayuguan where the Great Wall ends.