Nasdaq- and Toronto-listed Perpetua Resources is expecting the supplemental draft environmental impact statement (SDEIS) for its Stibnite project, in Idaho, to be open for public review in the fourth quarter.

The company reported on Tuesday that the United States Forest Service (USFS) had completed the cooperating agency review and that the SDEIS was currently progressing through final reviews in Washington DC.

The USFS is concurrently working with Idaho tribes to inform consultation.

Perpetua said it expected the additional evaluation contained within the SDEIS would show improved environmental outcomes that directly addressed issues raised during the public review of the 2020 draft DEIS and that the additional analysis and detailed review should lead to the USFS designating a preferred alternative in the SDEIS. This key designation would further narrow the scope of review for the remainder of the process.

The proposed Stibnite mine has been under scrutiny over fears that it would pollute Native American fishing grounds. Perpetua, however, says it plans to restore the site, which is an abandoned mining area. The company argues that redeveloping the already mined area will allow it to generate the funds needed to properly take care of the environment.

"We remain eager to show how our project improvements are designed to leave water quality and overall habitat in this historic mining district in better shape than they are in today," said president and CEO Laurel Sayer.

"Today, more than ever, a secure source of domestically produced antimony is essential for our national security and energy future. Perpetua is ready to be the responsible solution our country needs." 

Antimony is critical to the US defence industrial supply chain for materials ranging from ammunition to night vision goggles. Without a domestically mined source, the US is reliant on nations like China, Russia and Tajikistan that control 90% of the global supply. The Stibnite gold project has one of the world's biggest independent reserves of antimony and is positioned to provide a secure source of antimony for defence and commercial needs.

Congress recently authorised a 10% production tax credit for certain critical minerals, including antimony, in the Inflation Reduction Act. Antimony is a key component for the long-duration grid storage battery technology developed by Ambri. The Massachusetts-based company recently announced the expansion of its US manufacturing capacity along with a renewable energy demonstration project with Xcel Energy in Colorado.

In August last year, Perpetua entered into a partnership agreement with Ambri to provide antimony from the Stibnite project for battery production.