Lucara Diamond Corp discovered the 1,758-carat diamond, which is larger than a tennis ball and weighs close to 352g, just three years after making a separate record discovery in 2015.
The company struggled to sell the previouslydiscovered 1,109-carat “Lesedi La Rona” after it failed to meet its undisclosed reserve price at a June 2016 auction.
It was eventually bought for $53m (£41.1m) by British dealer Graff Diamonds nearly two years later.
The diamond was found in a mine in Botswana
According to Forbes, 67 finished gems were cut from the stone.
Following the latest find, Lucara’s shares rose as much as 11.4% to the highest in more than two months before closing up 6.3%.
The stone is second in size only to the famed 3,106-carat Cullinan Diamond, which was found near Pretoria in South Africa in 1905.
Two of the polished gems cut from the Cullinan – the Great Star of Africa and the Lesser Star of Africa – feature in the Crown Jewels of Britain.
Lucara says it has recovered a number of high value diamonds in Karowe since introducing new technology and has found 12 stones over 300 carats, including a 72-carat and a 327-carat diamond in April 2018.
Eira Thomas, the company’s chief executive officer, said: “Karowe has now produced two diamonds greater than 1,000 carats in just four years, affirming the coarse nature of the resource and the likelihood of recovering additional, large, high quality diamonds in the future.”
