LONDON (UPI) -- The world's largest uncut diamond has not sold at a London auction.

The Lesedi La Rona diamond, expected to sell for more than $ 70 million, fell notably short of the Sotheby's minimum reserve price. The auction was the first time such a large, rough diamond has been put on public sale.

The diamond is the size of a tennis ball and weights in at 1,109 carats. The gem was discovered in Lucara Diamond Corp's Karowe mine in Botswana last November and estimated to be more 2.5 billion years old.

The bidding reached $61 million, with the buyer's premium fee, it would have raised the total cost of the gem to about $68 million. Lucara sold an 813-carat rough cut diamond at a private auction for a record $63 million -- about $77,500 a carat -- last May.

Financial concerns over Britain's vote to exit the European Union might have been a factor in the diamond's failure to sell. Potential buyers likely thought cutting it into smaller stones would not yield enough value to justify such a high buying price.

"If you divide it by 1,109 carats, it is about $62,000 a carat," said Henri Barguirdjian, president and chief executive of Graff Diamonds. That is a very high price for a rough diamond, so obviously the reserve was too high.

Lucara announced it will be holding on to the gem for the time being.

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