A 2,492-carat raw diamond discovered in Botswana could be the second-largest gem-quality example ever unearthed.

The Canadian mining company Lucara Diamond Corp said it had recovered the “exceptional” stone from its Karowe diamond mine, with a photo showing the hefty rough diamond sitting in the cupped palm of a hand.

The largest gem-quality diamond ever discovered was the 3,106 carat Cullinan diamond, which was mined in South Africa in 1905 when it was still a British colony and gifted to King Edward VII. It was cut up into several gems, some of which are now part of the Crown Jewels.

Lucara’s president, William Lamb, said: “We are ecstatic about the recovery of this extraordinary 2,492-carat diamond.”

Lucara did not say what the value of the “high quality” diamond was or if it could be cut into gems. Botswana’s government said it was the biggest diamond discovered in the country.

Its Karowe mine has been yielding progressively bigger stones. In 2019, Lucara dug out the 1,758-carat Sewelo diamond, then the world’s second-biggest mined diamond. Louis Vuitton bought it for an undisclosed sum, even though it was black in appearance and it was unclear how many gems could be cut from it.

The 1,111-carat Lesedi La Rona diamond, also from Karowe, was bought by a British jeweller for $53m (£40m) in 2017.

The largest diamond ever found was the black Sergio stone, which was discovered above ground in Brazil in 1895 and cut up to be used in industrial drills. Black “carbonado” stones such as the Sergio are thought to be parts of meteorites.

Russia is the world’s largest diamond producer, but most large valuable finds have been made in Botswana in recent years. The southern African country has been trying to increase its power in the industry, negotiating a progressively bigger share of stones mined by Anglo American-owned De Beers last year, in a new 10-year agreement.

Botswana’s president, Mokgweetsi Masisi, will be one of the first people to see Lucara’s new, as yet unnamed, diamond before it is shown to the world at his office, the government said.