Newmont Mining Corp., the biggest U.S. gold producer, has agreed to sell its stake in Canadian Oil Sands Ltd. (TO: COS) for about C $608 million ($578 million).

Newmont owns about 6.5% of Calgary-based Canadian Oil Sands and will sell its stake to a banking syndicate that will then offer the shares to various buyers, Omar Jabara, a spokesman for Greenwood Village, Colorado-based Newmont, said in an email today.

“Our investment in Canadian Oil Sands has returned a lot of value for Newmont and its shareholders and this stake sale also will help streamline and rationalize our portfolio of assets,” he said.

Newmont is among gold companies that spent $195 billion on acquisitions in a decade-long bull market, which are now selling assets as the precious metal’s price tumbles. Whitecap Resources Inc. (TO: WCP), a Canadian oil and natural gas producer, said on June 27 it agreed to buy energy assets from Barrick Gold Corp., the world’s biggest gold producer.

Gold declined 26% in 2013, sliding into a bear market in April while equities and the dollar rose. Gold rallied for 12 years through 2012 as the U.S. Federal Reserve cut borrowing costs to a record to bolster the economy.

Copyright 2013 Bloomberg.

Divya Balji and Sonja Elmquist

www.bloomberg.com