Did it come from space? Can it really be one billion years old? No wonder this extraordinary gem, weighing about as much as a banana, is called The Enigma.
At 555.55 carats, the ancient black rock coming up for sale at auction is said to be the largest cut diamond in the world, with 55 faces, and is expected to sell for more than £4.4 million as I write.
It is certainly a phenomenon and one of the oldest items ever to come up for auction, although it is a mere youngster compared with the four billion-year-old meteorite that sold at auction in 2017 for a rather more modest £14,000.
As is widely known, diamond is one of the toughest substances known to man, having been forged deep within the Earth’s crust under intense heat and pressure so that the carbon atoms crystallise.
They are rare because so many of them remain hundreds of kilometres beneath the surface, although some emerge via magma.
Even rarer is the carbonado, black diamonds like this one that are especially tough and have only been found in Brazil and the Central African Republic.
So if diamonds are forged
In the bowels of the Earth, how come they think this one came from outer space?
Apparently it is because it also contains osbornite, or titanium nitride, a mineral so far found only in meteors. Perhaps, though, the osbornite was captured by the bubbling early planet when a meteorite crashed into it, then was transformed into the carbonado as the crust cooled and processed it. If so, The Enigma is documentary evidence of our home world’s earliest days.
