 The 14.62-carat ‘Oppenheimer Blue’ sold for a record $57.5 million on May 18, 2016. $ 3.93m per carat. | All coloured diamonds contain interstitial impurities or structural defects that cause the colouration. Pure diamonds are transparent and colourless. Type IIa diamonds can be coloured pink, red, or brown due to structural anomalies caused through plastic deformation during crystal growth. Color is considered the most important criterion in grading a blue diamond and determining its value. However, the most valuable of blue diamonds will also exhibit the highest clarity grades. |  The flawless 12.03-carat 'Blue Moon' Fancy Vivid Blue diamond was sold at Sotheby’s in Geneva on November 19, 2015, for $48.4m. $4m a carat. |
 The Zoe Diamond – $32,645,000 ($3,348,205 per carat) in 2015 | Type IIb diamonds, which account for 0.1% of gem diamonds, are usually light blue due to scattered boron within the crystal; these diamonds are also semiconductors. A blue-grey color may also occur in Type Ia diamonds and be unrelated to boron. While extraordinarily rare, blue diamonds are not the rarest. They are more uncommon than yellow diamonds, which have nitrogen in them, but they lose out in rarity to green, black, pink, orange, purple, and red.  |  The 10.10-carat De Beers Millennium Jewel 4 sold for $32 million in April of 2016. |
 | The Hope Diamond is 45.52 carats and is the largest deep-blue diamond known. The Golconda stone is considered to be the most famous diamond in the world. Now on display at the Smithsonian Natural History Museum in Washington, D.C. It is a Type IIb diamond and exhibits red phosphorescence after exposure to ultraviolet light. The diamond is notorious for being cursed. |  |
 | The Wittelsbach-Graff is a 31.06-carat, Fancy Deep Grayish Blue diamond with an IF clarity and an unusual cut with 82 facets. The stone sold in 2008 for $24.3 million. A 13.22 carat pear-shaped Fancy Vivid blue flawless diamond sold at Christie's Geneva on May 14, 2014 for $ 24m, setting a new world auction record at the time for a blue diamond. |  It was renamed 'The Winston Blue'. |
 The 14-carat symmetrical pear-shaped Blue Empress Diamond |  The 9.54 carat 'Shirly Temple Diamond', estimated at $ 25 - $ 35m failed to find a buyer. |  The 24.18 carat Cullinan Dream is a cut-cornered rectangular mixed-cut fancy intense blue diamond. $25.3m. |
 Emerald-cut, 5.69-carat fancy VVS1 vivid blue diamond made $15.1m in late 2017. |  A Graff crossover ring with two fancy vivid blue diamonds brought $12.5m in August 2017. |
