Auction house Sotheby's to accept cryptocurrency for 101-carat diamond

Auction house Sotheby's is breaking new ground by accepting cryptocurrency as payment for the auction of one of Earth's rarest diamonds.

Named "The Key 10138", the diamond weighs 101.38 carats and has been graded as "flawless".

It's anticipated to fetch more than US$15 million ($19.97 million) and for the first time ever, bidders can use cryptocurrency such as Bitcoin or Ethereum to buy it.

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"The Key 10138 is the first important diamond in the world to be auctioned with cryptocurrency as an accepted method of payment," Sotheby's writes.

"It was named to symbolise the unlocking of a new era in commerce and technology, and thus is a key to history.

"The Key 10138 will undoubtedly become a diamond that history remembers as it takes the culmination of humanity's work and knowledge on diamonds thus far, and turns the key to unlock a still more brilliant future."

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If the diamond sells for $20 million, it will cost in today's prices around 459 Bitcoin, or 7751 Ethereum.

Sotheby's says part of the key's appeal is its rare physical structure that makes it an anomaly even against some of the world's purest diamonds.

"There are only a small number of faceted diamonds that weigh over 100 carats throughout history and it is rarer to find such a diamond with perfect colour and clarity," the listing explains.

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"Type IIa diamonds are themselves very rare as they contain no IR-detectable nitrogen or boron impurities in their chemical structure and represent less than 2 per cent of all diamonds mined.

"Considered the most chemically pure diamonds, they tend to display exceptional transparency."

The diamond is set to go under the hammer on July 9 in Hong Kong.