The draft decision, said the USFS in a news release, comes after a “rigorous interagency permitting review, scientific evaluation, and public input” of the project’s modified mine plan of 2021, which proposed to restore the local fish habitat as well as improve the water quality through safe storage of legacy tailings.
In addition to USFS, Perpetua also had a clean-up agreement in place with the Environmental Protection Agency from 2021.
Following the USFS decision, there will be a 45-day objection period and another 45-day resolution period prior to the publication of the final record of decision, which USFS says is expected at the end of the year.
Altogether, the Stibnite project has undergone 14 years of scientific study, community engagement and engineering, eight years in the National Environmental Policy Act permitting process, and 150 days of formal public comment, during which 28,000 letters were received.
The Stibnite project is positioned to be one of the highest-grade open pit gold projects in the US with 4.8 million oz. of estimated reserves. The mine is expected to produce over 450,000 oz. of gold annually over the first four years with all-in sustaining costs under $450/oz., based on a 2020 feasibility study.
Antimony source
As a byproduct of gold production, the Stibnite project reserves also contain 148 million lb. of antimony, a critical mineral for national defense, clean energy and technology applications. The US currently has no domestic production of antimony.
Beginning on September 15, China, which is responsible for nearly half of all global mined output and dominates global refinement and processing, will begin restricting its exports of the mineral. Stibnite represents one of the largest reserves of antimony not under Chinese influence, and the only known US domestic reserve.
“We believe that the Stibnite gold project is a win-win-win,” said Jon Cherry, CEO of Perpetua Resources, in a press release Thursday. “It’s a win for Idaho, it’s a win for the environment, and it’s a win for America’s national security. Our independence from Chinese control over antimony is right here in our backyard.”
Due to its strategic importance, the Stibnite project has received major backing from the US government, including $75 million in awards from the Department of Defense. In April, Perpetua received a letter of interest from US EXIM for a $1.8 billion loan, which would be one of Washington’s largest investments ever in a domestic mine.
Feasibility study
According to the feasibility study published in 2021, Stibnite is expected to produce 4.2 million oz. of gold and 115 million lb. of antimony over a 15-year mine life, with the first four years making up a sizeable part of the production.
The project has an after-tax net present value (NPV) at 5% discount of $1.32 billion with an internal rate of return (IRR) of 22.3% and a payback period of just under three years. However, these figures would improve to $1.86 billion NPV, 27.7% IRR and 2.5-year payback when a higher gold price scenario is applied. Initial capital is estimated at $1.26 billion.
“Our project has exceptional economics, with an expected payback period of less than 3 years, while providing net environmental benefits and the critical mineral antimony. We have never been closer to unlocking the value of this unparalleled asset,” said Cherry in the release.
