Start saving your pennies. A blue diamond could bring close to $50 million at auction….it’s a rare 15.10-carat fancy vivid blue diamond. So how rare and unusual is this jewel? “Only 5- other vivid blue diamonds over 10 carats have ever come to auction according to Sotheby’s Asia. Known as the De Beers Cullinan Blue, the newly mined stone will be the largest vivid blue diamond to come to auction when it’s offered at Sotheby’s in Hong Kong in April. Currently holding the price record for a blue diamond sold at auction is the Oppenheimer Blue, a 14.62-carat fancy vivid blue diamond that sold for a staggering $57.5 million at Christie’s in May 2016.