A billion-year-old black diamond thought to have come from outer space is going up for auction, the BBC reports.
Named The Enigma, it is believed to be the largest cut diamond on earth and may have formed from a meteoric impact.
At 555.55 carats the gem is considered extremely heavy for a diamond, weighing about the same as a banana.
The rock is expected to fetch over $6m at a Sotheby’s auction in London by the time online bidding closes next week.
The gem is a carbonado, one of the toughest forms of natural diamond.
Black diamonds are usually about 2.6 to 3.2 billion years old – a time before dinosaurs existed.
The Earth itself is around 4.65 billion years old, so not much older than black diamonds.
Carbonados are extremely rare and have only ever been discovered in Brazil and the Central African Republic.
Because they contain osbornite, a mineral found only in meteors, they are believed to originate from space.
But their precise origins are shrouded in mystery.