Hecla Mining Co., of Coeur d’Alene, said this morning it has agreed to acquire Revett Mining Co., of Spokane Valley, in a stock transaction valued at $20 million.

The transaction is scheduled to be completed late in the second quarter and is contingent on approval by Revett shareholders.

Revett has two mining properties, the Rock Creek project and the Troy Mine, both in northwestern Montana.

Following the merger, Hecla plans to continue to pursue permitting at Rock Creek, a property the company describes as one of the largest undeveloped silver and copper deposits in North America. Rock Creek would tunnel underneath the Cabinet Mountains Wilderness Area, and the project has sparked opposition from environmental groups concerned about its potential impacts.

Phillips S. Baker, Hecla’s president and CEO, said in a press release, “Rock Creek is a world-class silver-copper deposit that we see becoming another Greens Creek (mine). Our experience of Greens Creek operating in a national monument in Alaska since 1997 will be invaluable as we take a patient and persistent approach to permitting and then responsibly operating the Rock Creek Mine.”

The Troy Mine, however, will be closed and reclaimed, meaning it will be restored to a more natural state.