(Corrects to show purchase not closed in headline, paragraph 1)
MOSCOW, Feb 17 (Reuters) - Russian tycoon Alexander Nesis' investment company ICT Group will close a deal by the end of the first quarter to buy about 25 percent of real estate investment firm O1 Properties from owner Boris Mints, a source close to the deal said.
The source said the deal could be valued at around $350 million.
Nesis, who with a fortune of $3.3 billion ranks as Russia's 30th richest man according to Forbes magazine, owns a minority stake in Russian precious metals miner Polymetal and his ICT group has assets in industries including finance and engineering.
Last year, he sold his 5.1 percent stake in potash producer Uralkali.
A representative for O1 declined to comment but confirmed talks are ongoing with ICT. A representative of ICT confirmed there were talks about the purchase of a stake but gave no further details.
It is unclear how much of a stake Mints has in O1 but he is the main shareholder. (Reporting by Olga Sichkar, writing by Megan Davies, editing by Elizabeth Piper)