The 390-carat diamond was unearthed in the Republic of Sakha in Russia’s far east.
“The found diamond is a light crystal of an irregular shape, bordered by a yellow-brown halo – a combination of mass, shape and colour that is unique today,” Alrosa said in a statement.
Before this discovery, the largest gemstone-quality diamond discovered in Russia was a 401-carat stone earthed in 2013.
In August, Alrosa released its first financial report since the invasion of Ukraine in February of last year.
Sales increased to RUB188.16 billion ($AU3.02 billion) for the six months, a modest improvement from RUB187.16 billion ($AU3 billion) the previous year. Profit declined by 35 per cent.
Alrosa has also confirmed that construction of a new $US1.26 billion ($AU1.97 billion) mine is underway, with production expected to begin in 2032.
Reserves of 173.5 million carats have been identified at the new mine, known as the Mir-Gluboky project.
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