Toronto-based Barrick Gold launched its tailings reprocessing project at its Golden Sunlight past-producing mine in Montana.
The new facility will reprocess the ground rock to remove sulphur. This sulphur will be sold and used in production at Nevada Gold Mines, which is majority-owned and operated by Barrick.
"We look forward to shipping the first concentrates within weeks," Barrick Gold chief executive Mark Bristow said.
The removal of sulphur from the tailings rock will also eliminate a potential source of groundwater contamination.
The remaining material following the tailings reprocessing will be used as backfill at the Mineral Hill pit.
The process of opening the facility took one year, and has so far generated 75 jobs, Bristow said.
Montana Governor Greg Gianforte credited the state government's willingness to work with Barrick in enabling the mining company to open the facility so quickly.
"This project is an example of what's possible when state agencies provide a stable, predictable regulatory process that companies like Barrick can rely on," he said.
Golden Sunlight produced gold for nearly 40 years, producing more than 3 million ounces in total. Barrick shut down the mine in 2019 when it was no longer economically viable to produce gold.
Under Montana law, mining companies must responsibly rehabilitate its mines. Mine companies that fail to do so, and which managed mines that continue to emit effluent or otherwise harm the environment post-closure, will not be allowed to apply for mining permits in the state.