The biggest uncut diamond to be discovered in over a century failed to sell at a Sotheby's auction on Wednesday, but the chief executive of Lucara Diamond Corp, the company that found the gem, said there was interest from buyers in the diamond trade.Bids for the 1,109-carat, tennis ball-sized stone topped out at $61 million - an amount that fell short of the undisclosed minimum reserve price.Sotheby's had estimated that the diamond, found last November at Lucara's mine in Botswana, would sell for more than $70 million."The fact that the stone didn't sell, yes, it is disappointing but it doesn't change anything for Lucara as a company," Lucara CEO William Lamb said in a telephone interview from London."There is definitely demand for the stone. It is just demand from the people who we would normally sell the stone to," he said.

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