(IDEX Online) - Sotheby's Hong Kong could make cryptocurrency history when it auctions a 101.38-carat diamond next month.Buyers will have the option of paying in Bitcoin or Ethereum.That means the stone could set a record as the highest-priced diamond - or indeed any physical object - ever to be sold in a crypto-transaction.The high estimate is $15m - equivalent to BTC515 or ETH8787 at today's exchange rates."This is a truly symbolic moment," said Patti Wong, chairman of Sotheby's Asia, in a statement."The most ancient and emblematic denominator of value can now, for the first time, be purchased using humanity?, ?s newest universal currency."The pear-shaped D-color, flawless, Type IIa diamond, named The Key 10138, is one of fewer than 10 weighing over 100-cts ever offered at auction, said Sotheby's.It will be sold in a single-lot auction on 9 July. Payment can also be made in traditional money.Pic courtesy Sotheby's