BOISE, Idaho (AP) — Federal land managers on Thursday approved 10 more years of mining and a 500-acre expansion on public land in central Idaho for one of the largest molybdenum mines in the world.

The U.S. Bureau of Land Management and U.S. Forest Service each issued decisions allowing the work at Thompson Creek Mine about 20 miles southwest of Challis. At a mile wide and half a mile deep the open pit mine is the fourth-largest mine producing primarily molybdenum, though it falls a few notches when mines that also produce copper are included.

The mine is on private land but needed federal approval to use public land for waste rock and tailings. Molybdenum is used as an alloy to make steel, cast iron and other metals.