By Scott Patterson 

Swiss mining giant Glencore PLC agreed to pay $534 million in cash to acquire stakes in two African copper projects held by its longtime and controversial business partner, the Israeli billionaire Dan Gertler.

Glencore said it would purchase the 31% holding held in Mutanda Mining by Mr. Gertler's Fleurette Group, valuing the stake at $922 million. The amount of cash being paid was reduced by settlement of loans owed by Fleurette to Glencore.

Glencore will also purchase Mr. Gertler's minority holding in Katanga Mining Ltd., a deal that values the stake at $38 million.

The investment in the copper mines in the Democratic Republic of Congo is the most significant outlay by Glencore since its stock was roiled by a bust in commodity prices in 2015, when investors grew worried about its massive debt load. The turmoil pushed Chief Executive Ivan Glasenberg, one of the mining industry's most aggressive deal makers, onto the M&A sidelines as the company pared back debt and sold off assets.

Now Mr. Glasenberg looks emboldened by a surge in Glencore's stock and rising commodity prices and appears to be back in the hunt. Talks about the Congo deal have been going on for months, according to a person familiar with the matter. In December, Glencore agreed to pay EUR300 million ($318 millon) for a stake in Russian oil giant PAO Rosneft.

The purchase of Mr. Gertler's mining stakes increases Glencore's output of copper, which has rallied this year in part because of labor disputes at some of the world's largest copper mines. Copper prices edged up 0.5% to $2.7820 a pound, its highest point since late May of 2015.

The deal also distances Glencore from Mr. Gertler, a magnet for controversy since he started operating as a diamond merchant in the Congo in the late 1990s. Mr. Gertler became a close partner with Glencore in the Congo a decade ago through investments in copper assets eventually owned by Katanga Mining.

Mr. Gertler was at the center of the Justice Department's criminal case against New York hedge fund Och-Ziff Capital Management LLC. The Justice Department claims that Mr. Gertler paid more than $100 million in bribes in the Congo, including $10 million to President Joseph Kabila, to facilitate mining deals. Mr. Gertler, through a spokesman, has denied the allegations, which have not resulted in formal charges being filed.

"We are extremely proud of what we have achieved at Mutanda," Mr. Gertler said in a statement. "Together with Glencore, Fleurette has enabled the mine to deliver on its full potential and it has become one of the largest taxpayers in the DRC."

The $534 million payment comes after settlement of $556 million of loans payable by Fleurette to Glencore. Glencore also acquired $130 million of shareholder loans owed to Fleurette by Mutanda.

Glencore said it now owns 100% of Mutanda and 86.3% of Katanga's shares. Katanga trades on the Toronto Stock Exchange.

Details of the deal were first reported by Bloomberg.

Write to Scott Patterson at scott.patterson@wsj.com

(END) Dow Jones Newswires

February 13, 2017 14:00 ET (19:00 GMT)