The "Ocean Dream" 5.5-carat fancy vivid blue-green diamond sold for a record $17.3 millionChristie'sThe “Ocean Dream,” the largest fancy vivid blue-green diamond known to exist, sold Wednesday for $17.3 million at the Christie's Magnificent Jewels auction at the Four Seasons Hotel des Bergues in Geneva. At nearly $3.5 million per carat, it set a world record price for a diamond of its type.The 5.5-carat triangular-shaped diamond sold after a bidding battle lasting about 20 minutes among three collectors, according to Rahul Kadakia, who spoke with me immediately after the auction,.The same diamond was previously sold by Christie’s in May 2014, when it achieved $8.6 million.“We were very happy to have had the pleasure of selling this stone for the second time,” Kadakia said. “It made a world record price. We’re having a good season.”The 5.5-carat 'Ocean Dream' without its fitting. Christie'sTom Moses, the Gemological Institute of America’s EVP and chief laboratory and research officer, personally evaluated the diamond and issued its report. He noted that, adding to its rarity, the stone is a Type Ia diamond, among the purest categories of natural gems, with an SI1 clarity grade. In a letter, Moses said the Ocean Dream is the largest fancy vivid blue-green diamond ever graded by the GIA laboratory.MORE FOR YOUIn an email following the sale, Moses explained that the blue-green hue is believed to result from natural radiation exposure near the Earth’s surface, with the color often concentrated close to the outer layers of the stone. As a result, the diamond required an unusually precise cutting and polishing process to preserve its color.The Ocean Dream first appeared publicly in the Smithsonian Institution National Museum of Natural History’s “Splendor of Diamonds” exhibition. It was displayed alongside other rare colored diamonds in what was described as a “rainbow of colors” featuring red, orange, yellow, pink, blue, blue-green and white diamonds.All but one lot sold in the 87-lot auction, which achieved a total of $66.5 million.“The auction was very hot,” Kadakia said. “Everything did great.”Signed jewels and Kashmir sapphires were among the strongest performers, with many lots exceeding estimates.1920 necklace composed of two strands of graduated natural pearls fetched $5.3 millionChristie'sKadakia noted that the second-highest lot had an exceptional result as well. It was a circa 1920 necklace composed of two strands of graduated natural pearls ranging from approximately 12.70mm to 7.40mm, accented by old and baguette-cut diamonds with a 14kt white gold clasp. The necklace sold for $5.3 million, nearly four times its high estimate.A Chaumet ring with a 22.28-carat unheated Kashmir sapphire fetched $3.5 millionChristie'sThe third-highest lot was a ring by Chaumet centered with a 22.28-carat unheated Kashmir sapphire exhibiting the rare “Royal Blue” hue. It sold for more than $3.5 million, surpassing estimates.Other highlights included:A circa 1910 platinum ring centered with a fancy vivid orange-yellow cushion brilliant-cut diamond, flanked by old, single-cut and round diamonds, sold for more than $2.2 million, below estimates. An unsigned platinum and 18kt yellow gold multi-diamond floral necklace attributed to Fred sold for more than $1.8 million. The piece featured four fancy intense yellow cushion rectangular modified brilliant-cut diamonds, two fancy yellow cushion rectangular modified brilliant-cut diamonds, a pear brilliant-cut diamond, marquise brilliant-cut diamonds and additional pear-shaped and round diamonds. A Bulgari platinum ring centered with a 9.82-carat octagonal unheated Kashmir sapphire displaying a “Royal Blue” hue sold for more than $1.7 million, more than double its high estimate.A Boucheron multi-gem Art-Deco necklace fetched $1.5 millionChristie'sA 1920s Art Deco “Scarf” necklace by Boucheron fetched more than $1.5 million, triple its high estimate. The multi-gem design featured buff-top rubies and emeralds, onyx baguettes and old and single-cut diamonds. The necklace can be detached into four sections and worn as a choker and two bracelets. Drop earrings by Van Cleef & Arpels featuring cushion rectangular modified brilliant-cut diamonds weighing 19.33 and 18.03 carats, surrounded by pear brilliant-cut white diamonds, sold for more than $1.3 million. A Cartier Art Deco multi-gem platinum and 18kt yellow gold “Tutti Frutti” clip brooch sold for more than $1.3 million, nearly double its high estimate. The brooch featured a carved central emerald, emerald and sapphire beads, cabochon and oval-shaped sapphires, cabochon rubies and round and single-cut diamonds.