Lucara Diamond Corp. said it unearthed the stone — roughly the size of a tennis ball — at its Karowe project in Botswana, a mine renowned for its huge gems including the previous holder of the No. 2 position. Still, the company said the diamond is a near gem of variable quality, meaning it won’t yield incredibly valuable polished diamonds on par with earlier finds.

Lucara’s Karowe mine is becoming famous for giant stones. In 2015, Lucara found the 1,109-carat Lesedi La Rona, which at the time was the second-largest ever and eventually sold for $53 million. The mine has also yielded a 813-carat stone that fetched a record $63 million. Those two gems were both much more valuable Type-IIa stones.

Still, the latest find shows that Karowe’s plant can process and detect huge gems without breaking them, a consistent headache when trying to separate brittle stones from hundreds of tons of waste rock.

“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,” Eira Thomas, Lucara’s chief executive officer, said in a statement.

Lucara, based in Vancouver, Canada, rose as much as 12 percent, the most in a year.

The biggest diamond ever discovered is the 3,106-carat Cullinan, found near Pretoria in South Africa in 1905. It was cut into several polished gems, the two largest of which — the Great Star of Africa and the Lesser Star of Africa — are set in the Crown Jewels of Britain.