Debswana Mining Company, owned by De Beers and the Botswana government, said on Tuesday it has terminated a $1.3 billion contract with a unit of Australia’s Thiess to extend the lifespan of its Jwaneng diamond mine and will carry out the project in-house. Debswana, among the world’s largest diamond producers, declined to provide a reason for terminating the contract for the extension project, known as Cut 9, which was awarded to Majwe Mining in 2019. The nine-year project is expected to extend the life of Debswana’s flagship mine to 2035, yielding an estimated 53 million carats of rough diamonds. “The…