A 555-carat black diamond is going up for auction at Sotheby's. Nicknamed 'The Enigma,' the extremely rare gem is believed to be billions of years old and to have originated in space, from either a meteor or asteroid. A Sotheby's rep called the auction 'a once-in-a-lifetime opportunity to acquire one of the rarest, billion-year-old cosmic wonders known to humankind.'

According to the auction house, previous black diamonds have been sold at a cost of approx $13k per carat, meaning this baby could be had for a price of $7.5M when all is said and done.