RESEARCH INTO POST-FLOTATION PROCESSING OF ANTIMONY TRISULFIDE CONCENTRATES FOR PREPARATION OF MILITARY GRADE PRIMERS

This proposal outlines a general approach and potential investigation path focused on development of a high-grade stibnite concentrate suitable for further testing and evaluation for use in military grade primers utilizing materials sourced from the Stibnite Gold Project (SGP) site located in Valley County, Idaho. Previous SGP beneficiation (crushing, grinding, flotation, cleaning) test work was designed to optimize recovery of gold and the bulk of the antimony contained in SGP ores.  However, this work did not investigate development of a process to develop high grade stibnite concentrate suitable for ammunition primers which is the focus of this project. The SGP site was a major past producer of antimony and tungsten providing 90% of the antimony demand and 50% of the tungsten demand for the U.S. during World War II. The SGP is in the advanced stages of federal and state permitting for mine development and will, once in production, provide on average 35% of overall U.S. demand for antimony for the first 6-years of operations.  The large size and grade of the deposits in the SGP will make DoD and commercial antimony trisulfide consumers less vulnerable to supply chain disruptions. The majority of the world’s antimony supplies, and processing facilities are located in China, Russia and Tajikistan and other deposits and processing facilities around the world are often under direct or indirect control of these entities, which are fundamentally unfriendly towards U.S. interests. The lack of antimony mines and processing facilities in North America is not a new problem and has resulted in the listing of antimony on watch lists of various federal government agencies and departments, including recently the Department of Interior (DOI) Critical Minerals List (USGS, 2022), and since World War II the Department of Defense, Defense Logistics Agency (DLA, 2022 watch lists for critical and strategic materials. There are significant risks to DOD’s ability to obtain suitable sources of high-quality antimony trisulfide for munitions use due to foreign control of upstream (mines), mid-stream (processing facilities) and to a lesser extent, downstream (manufacturing) ends of the supply chain. The primary goals of the Phase I investigations are to demonstrate that a high-grade antimony trisulfide product can be generated from SGP antimony ores through bench-scale flotation recovery of an antimony-rich sulfide concentrate, cleaning of that concentrate, and generation of three initial test samples of approximately 5 pounds of material each for further evaluation for military munitions applications. The longer-term objective is to then advance technical studies to a Phase II study to develop a flowsheet for generation of a larger pilot-scale sample of approximately 500 pounds of high-grade antimony trisulfide for additional evaluation.