Private company Sunshine Silver Mining and Refining (SSMRC) has announced plans to revive one of the US's most storied silver mines and build the country’s only large-scale, permitted antimony refinery.

The company, backed by billionaire Thomas Kaplan’s Electrum Group, is targeting first production in 2028 from the Sunshine project, which is envisioned as the sole fully integrated US operation producing and processing silver, antimony, gallium and germanium.

“SSMRC is uniquely positioned to become a major US hub for critical minerals mining and processing,” CEO Heather White said. “In addition to producing its own metals, the project will also be capable of processing third-party concentrates, benefiting from our refining capacity.”

While the company closed a $75-million equity financing round in September, led by its majority shareholder Electrum Silver US, the real focus is on accelerating development of the Sunshine mine and its associated refinery. The project already benefits from more than $600-million in existing infrastructure and $250-million in prior exploration and development spending since Electrum acquired the asset in 2011.

The Sunshine refinery, already permitted to process multiple metals, is being upgraded to handle antimony – a mineral deemed essential for US national security and energy resilience. The facility could supply about 40% of the US's yearly antimony demand by 2028, rising to as much as 80% by 2031, according to company projections.

Antimony, used in munitions, semiconductors, and grid storage batteries, is currently imported almost entirely from China and Russia. The US government has identified it as one of the highest-priority minerals for domestic sourcing under recent executive orders to bolster supply chain security.

The Sunshine project also contains one of the world’s highest-grade undeveloped silver deposits, with indicated resources of 112-million ounces grading 1 067 g/t. Production in the first five years is forecast at more than 7.6-million ounces of silver a year – enough to lift total US output by 20% or more.

Located in Idaho’s historic Silver Valley, the Sunshine mine has produced more than 360-million ounces of silver since the early twentieth century. Electrum has expanded Sunshine’s land position fourfold since its acquisition and now holds the largest mineral rights package in the district. Exploration drilling has identified several new silver-rich zones, suggesting potential for resource growth beyond the current mine plan.

In parallel with the antimony plant, SSMRC is progressing engineering and feasibility work to restore the mine’s hoisting system, surface facilities, and water treatment infrastructure. A feasibility study is targeted for early 2027.