As billionaire investor George Soros asserts on his latest book tour that oil and other commodities are over -priced, Soros has been quietly investing in a number of energy companies.

The uber investor also bought nearly 3.2 million shares of Brazilian mega-miner Vale, reduced his holdings of Southern Copper and the Potash Corp. of Saskatchewan, and dumped his shares of Stillwater Mining, according to Soros Fund Management SEC 13F filings reported during the first quarter of this year.

However, Soros was bullish on mining equipment, adding new shares purchases of Bucyrus International (298,156 shares) and Joy Global (322,500 shares) to his holdings. He had previously sold out his Bucyrus shares.

Soros Fund Management reduced its holdings in the Potash Crop. Of Saskatchewan by 75% to 65,500 shares and also reduced its Southern Copper shares by 39.67% to 3,020 shares.

Shares of U.S. PGM miner Stillwater Mining were sold out by the fund, along with Chevron shares, according to the website

Meanwhile, Soros added a number of energy and utility investments to his portfolio including 998,500 shares of Talisman Energy, and 656,023 shares of Alpha Natural Resources among others.

While Soros told the BBC that he believes oil and other commodities are over-priced, he sees little chance of the price of oil going down until there is a big slowdown in richer economies.

The private investment fund (Quantum) that Soros Fund Management administers reported a 34% return last year.