American Tungsten & Antimony (ASX:AT4) reports 99.8% antimony as US government discussions advance
American Tungsten & Antimony has reported a 99.8% antimony result from an ingot sample produced at the Del Sol Refinery in Nevada using material mined at White Spar in Arizona.
The sample met every chemical requirement of ASTM B237 Grade A, while the company attended White House meetings in pursuit of funding and offtake arrangements and hosted Members of Congress at both sites.
Highlights
Sample S-260930-294 exceeded the 99.65% Regulus II grade and met the 99.8% minimum for ASTM B237 Grade A.
The remaining 4 samples returned 99.5% to 99.6% antimony under earlier process conditions.
AT4 is assessing the addition of a tungsten ammonium paratungstate circuit at Del Sol.
The acquisition of Nexus Metals, which holds rights relating to White Spar and Del Sol, remains incomplete.
The ingot was produced from antimony flake derived from material mined at the White Spar Antimony Mine in Yavapai County, Arizona, and refined to metal at Del Sol in Amargosa Valley, Nevada.
The refinery is constructed and permitted, using a hydrometallurgical process comprising alkaline leach and electrowinning.
NSL Analytical Services in Cleveland, Ohio, analysed drill shaving samples from 5 different ingots.
Impurities were determined by ICP-MS, sulphur by pyrohydrolysis followed by ion chromatography, and mercury by cold vapour atomic absorption, with antimony determined by difference consistent with ASTM B237 and standard industry practice.
ASTM B237 sets chemical requirements for refined antimony in ingot, pig or cake form, with Grade A requiring a minimum of 99.8% antimony and Grade B requiring 99.5%.
The highest assay was obtained from material produced using optimised electrowinning conditions, whereas the other samples were produced before those conditions were applied.
AT4 states that optimised electrowinning, together with subsequent fire refining, is expected to produce ingot consistently at grades exceeding Regulus II.
However, the results relate only to the individual samples tested and may not represent all ingot produced during the restart campaign, while future production is not assured to meet the specified grades.
AT4 Chief executive Casper Adson commented,
“Exceeding the Regulus II grade and producing ASTM B237 Grade A with Arizona mined material at the Del Sol Refinery in Nevada is a significant result for AT4 and for the United States.”
Executive director of government relations and marketing Andre Booyzen joined the World Trade Center Utah delegation for roundtable meetings on 5 October 2026, hosted by the Office of the United States Trade Representative and the White House.
Discussions focused on AT4 pursuing further US government funding and offtake arrangements.
Congressional visits followed on 6 and 8 October, with Paul Gosar joined at White Spar by House Committee on Natural Resources chairman Bruce Westerman and Congressman Eli Crane.
The announcement specifies that the meetings and visits constitute neither government endorsement nor commitments to funding, offtake or other commercial arrangements.
AT4’s stated strategy is to develop a US supply chain for antimony and tungsten, against the context of antimony’s US critical mineral designation and China’s introduction of export controls in 2024.
Its assessment of a tungsten circuit at Del Sol remains an identified activity, although AT4 does not currently own or control either asset.
The release reports no metallurgical recovery, production rates or volumes.