The Canada-based diamond miner has been using X-ray technology to pinpoint large diamonds and sort them without breaking them apart.
William Lamb, the firm’s chief executive, said: “We are ecstatic about the recovery of this extraordinary 2,492 carat diamond.
“This find not only showcases the remarkable potential of our Karowe Mine, but also upholds our strategic investment in cutting-edge XRT technology.”
He said Lucara was in no hurry to cut, polish or sell the stone and it would take some time to assess it fully.
While industry sources predicted it was most likely to be eventually sold to a large jewellery or fashion house, he said there were many options, including private collectors and museums.
Previous sales had taught him that “there are many, many people out there with large amounts of money,” he told the Telegraph.
“We need to think outside of the box when it comes to something of this historical significance.
“I think with this one there is no one in living memory who has ever seen a stone of this magnitude and it’s those kinds of things which make it special.”