AT4 puts a number on its Del Sol ingot

American Tungsten & Antimony has published the purity figure it held back on 21 September. One of five ingots made at the Del Sol refinery in Nevada assayed 99.8 per cent antimony, the minimum for Grade A under ASTM B237. The other four fell short of the commercial Regulus II grade.

The assay answers one question left by the first Del Sol ingot. Who owns the refinery, and who will buy its metal, are still unsettled.

On 13 October 2026 American Tungsten & Antimony (ASX: AT4) reported assays for five antimony ingots poured at the Del Sol refinery in Amargosa Valley, Nevada, from flake derived from ore mined at the White Spar mine in Yavapai County, Arizona. One of them, sample S-260930-294, returned 99.8 per cent antimony. AT4 says that meets every chemical requirement of Grade A under ASTM B237, the standard specification for refined antimony in ingot, pig or cake form, and beats the 99.65 per cent minimum of Regulus II, a commercial grade. The other four came in between 99.5 and 99.6 per cent. The company says those four were made under earlier process conditions, before the optimised electrowinning conditions applied to the fifth.

AT4's announcement of 21 September 2026, which reported the first ingot from Del Sol, gave no grade, purity or metallurgical recovery while independent testing continued. The new assays were run by NSL Analytical Services in Cleveland, Ohio, on drill shavings from each ingot. Impurities were measured directly, and the antimony content was calculated by difference, as the share left once the measured impurities are subtracted, which AT4 says is the basis ASTM B237 uses and standard industry practice.

For the best sample, against Regulus II and Grade A, on selected elements:

Source: American Tungsten & Antimony, ASX announcement of 13 October 2026, Table 2.

The result rests on a single sample. AT4 expects the optimised electrowinning conditions, followed by fire refining, to produce ingot above Regulus II consistently, but it states that the assays apply only to the samples tested and may not be representative of all ingot produced during the restart campaign. It gives no assurance that future production will meet Grade A, Grade B or Regulus II, and still reports no metallurgical recovery, production rate or volume.

The grade is for metal, measured against a commercial standard. ASTM B237 is not MIL-DTL-159E, the military specification for antimony sulfide that this publication set out on 3 October in its comparison of six routes to antimony for the United States, and an ingot is different from trisulfide.

Nor has ownership moved. AT4 still neither owns nor controls Del Sol or White Spar. Its claim on both runs through its agreed acquisition of Nexus Metals, which holds option and earn-in rights over the two assets. Shareholders approved that deal on 21 September 2026, and it had not completed when the assays were published.

The rest of the announcement concerns Washington. On 5 October 2026 Andre Booyzen, AT4's executive director of government relations and marketing, joined a World Trade Center Utah delegation at roundtable meetings hosted by the White House and the Office of the United States Trade Representative. He met Ambassador Jamieson Greer, the trade representative, David Copley of the National Security Council and George Kollitides of the Office of Strategic Capital, in talks the company says focused on funding and offtake arrangements with the US government. On 6 and 8 October Congressman Paul Gosar visited White Spar and Del Sol, joined at White Spar by Bruce Westerman, chairman of the House Committee on Natural Resources, and Congressman Eli Crane. AT4 states that neither the meetings nor the visits amount to an endorsement or to any commitment of funding or offtake.

AT4 also cites Executive Order 14415, signed on 20 July 2026. It orders the Secretary of War to require defence contractors to trace their materials back to the origin of the raw materials. On acquisitions he identifies, contractors relying on a supplier controlled by China, Russia, North Korea, Iran or another nation the Secretary designates must qualify an alternative. Its tightening of sourcing waivers applies only to the materials listed in 10 U.S.C. 4872, which does not include antimony at present. This could change moving forward. The order also gave the Secretary 90 days, to 18 October 2026, to produce a strategy for speeding up the testing and qualification of new sources.

According to AT4, the grade lets it talk directly to the Defense Logistics Agency, to Project Vault and to defence primes. The Defense Logistics Agency manages the National Defense Stockpile, and in September 2025 it awarded United States Antimony a contract of up to $245m for antimony ingot. Project Vault, launched on 2 February 2026 with an Export-Import Bank loan of up to $10bn, establishes the US Strategic Critical Minerals Reserve, a public-private partnership that stores raw materials for manufacturers. One is a defence stockpile and the other an industrial one, though the same order anticipates it selling to defence contractors as well. The announcement records a commitment from neither. AT4 is, however, already negotiating with one federal agency: on 18 August 2026 the Department of Energy selected its US subsidiary, Trigg Minerals, to negotiate a potential award of up to $18m for antimony smelting capacity, a selection that has yet to become an award.

AT4 has said its work at Del Sol depends on completing the Nexus deal. Completion would bring under its control the refinery that made the Grade A ingot. Once AT4 proves that grade can be repeated across production, a stockpile contract of the kind United States Antimony won in September 2025 could come within reach.