Alrosa has recovered a 390.7-carat diamond from its Mayat mine in Yakutia, the largest gem-quality rough discovered in Russia in 10 years.

The stone is irregularly shaped, bears a light color, and is bordered by a yellow-brown halo, the company said Sunday. The miner found the diamond during the night-washing of rough from the Ebelyakh portion of the deposit, along with a colorless diamond with a traditional octahedron shape weighing 37.7 carats.

In 2013, Alrosa found a gem-quality, 401-carat rough, it noted.

“The discovery of one of the largest diamonds in Russian history is undoubtedly an unprecedented event and an excellent finale to the 2023 mining season,” said Alrosa CEO Pavel Marinychev. “Experts have yet to study in detail and evaluate the potential of the mined diamond and its characteristics, but, without a doubt, this is a record holder both for our company and for the country’s diamond industry.”

In August, the miner released its first results in over a year. Sales increased marginally to RUB 188.16 billion ($1.9 billion) for the first half of the year, compared to RUB 187.88 billion ($1.9 billion) a year earlier. Profit slid 35% to RUB 55.57 billion ($562.5 million). The company stopped publishing its results in March 2022 after the war in Ukraine cut off the business from much of the global industry.