Art house Sotheby’s just sold off a billion-year-old black diamond for $4.3m. The 555.55-carat gem named The Enigma is believed to be the world’s largest cut diamond. It weighs about the same as a banana. It had been expected to sell for more than $5m when it went on sale. Some scientists suggest that the gem was carried to Earth by an asteroid. Its new owner is entrepreneur Richard Heart who purchased it using cryptocurrency. He decided to rename it the “ diamond,” after the blockchain platform he created. The gem is a carbonado, one of the strongest forms of natural diamond. It contains osbornite, a mineral found only in meteors, which makes many believe that Enigma came from space. Carbonados are extremely rare and have been discovered in only two regions of the world—Brazil and the Central African Republic. Where black diamonds come from remains a mystery. They are considered to be around 2.6 to 3.2 billion years old – a time before dinosaurs existed.