RAPAPORT... A blue diamond weighing 5.53 carats failed to find a buyer at Sotheby's Geneva on Wednesday despite being billed as the star of the auction. The cushion brilliant-cut, fancy-vivid-blue diamond is part of an eight-piece group called the De Beers Exceptional Blue Collection, which Sotheby's has spread between its various Magnificent Jewels sales. No bids matched the stone's threshold price for sale, according to a post-auction report by the Fancy Color Research Foundation (FCRF). The piece carried a presale estimate of $11 million to $15 million."The blue is an exceptional stone in every sense," Sotheby's told Rapaport News Thursday. "It attracted significant interest prior to yesterday's sale. While we didn't get to see it sell in the room last night, we are confident it will find a new home very soon."Meanwhile, a number of items set records at the November 9 sale, including a 20.16-carat sapphire and diamond ring from Cartier. That piece, which fetched $2.8 million against a high estimate of $2 million, saw a record price per carat for any blue sapphire of Burmese origin ever sold at auction. A 20.58-carat, pink sapphire ring also broke the record for per-carat price, bringing in $1.9 million, or $91,690 per carat, well above its $808,368 upper price tag. A pink sapphire and diamond brooch weighing 92.01 carats by Jean Schlumberger sold for $1.8 million, outstripping its $505,278 high estimate and setting a record price for a piece of jewelry by the designer.Another notable item at the sale was a pair of unmounted oval-cut, D-flawless diamonds weighing 20.03 and 20.19 carats. The duo fetched $4.2 million, within estimates. A step-cut, 33.13-carat, D-color, VVS1-clarity diamond ring by Cartier brought in $2.9 million, also within its expected range. The entire Geneva Magnificent Jewels auction garnered $50 million. Sotheby's will offer two more blue diamonds from the De Beers collection at its upcoming New York Magnificent Jewels sale on December 7.Image: The 5.53-carat De Beers blue diamond. (Sotheby's)