Black Diamonds

A billion-year-Old Black Diamond thought to have come from Outer Space is going up for auction.

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 £4. 4 m ($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.

Aaron Celestian, a geologist at the Natural History Museum of Los Angeles , said that carbonados " could have formed super deep within The Earth 's interior, far deeper than what we know already of diamonds.

" There are hypotheses that suggest they were formed at impact sites where a large asteroid fell on earth, " he told Reuters news agency.

A competing theory is that Black Diamonds may have formed in Outer Space before falling to The Earth .

Sotheby's is describing the sale as a " once-in-a-lifetime opportunity to acquire one of the rarest, billion-year-Old wonders known to humankind. "

As well as weighing exactly 555. 55 carats, The Diamond has been cut to display 55 facets or faces.

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Source of news: bbc.com