ASX: AT4 | OTCQB: ATALF | 14 October 2026
AT4 Hits 99.8% Antimony at Del Sol, Clearing Regulus II and ASTM Grade A
Antimony ingot produced at the Del Sol Refinery in Nevada from ore mined at the White Spar Antimony Mine in Arizona has returned 99.8% antimony, exceeding the 99.65% Sb Regulus II commercial grade and meeting the 99.8% Sb minimum of ASTM B237 Grade A, the highest grade under that specification. This is independently assayed metal, produced from US ore on US soil.
Antimony ingot produced at the Del Sol Refinery. Image: American Tungsten & Antimony Ltd, ASX announcement 13 October 2026.
Why This Result Matters
Every AT4 announcement before September described intent, engineering or federal process. The September restart campaign produced metal. This announcement puts a number on that metal, verified by an independent laboratory, and the number clears both relevant commercial benchmarks.
Product qualification with defence primes and government agencies cannot begin without physical samples at specification. AT4 now has both.
The Numbers
Five ingots were sampled. The first four were produced under earlier process conditions, before the optimised electrowinning conditions applied to sample 294.
| Sample ID | Sb (%) | Process condition |
|---|---|---|
| S-260930-290 | 99.5 | Earlier conditions |
| S-260930-291 | 99.6 | Earlier conditions |
| S-260930-292 | 99.6 | Earlier conditions |
| S-260930-293 | 99.6 | Earlier conditions |
| S-260930-294 | 99.8 | Optimised electrowinning |
Sb = antimony. Results reported by NSL Analytical Services, Inc.
The Company states that the optimised electrowinning conditions, together with subsequent fire refining, are expected to consistently produce ingot at grades in excess of Regulus II. That is an expectation, not a result.
Grade A is not a single antimony threshold. It sets maximum limits for each impurity, and sample S-260930-294 met all of them.
| Element | Regulus II max | ASTM Grade A max | S-260930-294 | Status |
|---|---|---|---|---|
| Sb, min | 99.65% | 99.8% | 99.8% | Both met |
| Pb | 1,500 ppm | 1,500 ppm | 1,300 | Met |
| As | 1,000 ppm | 500 ppm | <50 | Met |
| S | n/s | 1,000 ppm | <10 | Met |
| Cu | 500 ppm | 500 ppm | 70 | Met |
| Ni | 500 ppm | 500 ppm | 220 | Met |
| Fe | 300 ppm | 500 ppm | <10 | Met |
| Se | 50 ppm | 500 ppm | <50 | Met |
| Te | 20 ppm | 500 ppm | <10 | Met |
| Bi | 20 ppm | 500 ppm | <10 | Met |
| Na | n/s | 500 ppm | 80 | Met |
| Al, Cd, Cr, Hg, Sn, Zn | n/s | 500 each | <10 each | Met |
n/s = not specified. Figures as reported in the Company’s announcement of 13 October 2026.
Drill shaving samples from five different ingots were analysed by NSL Analytical Services, Inc. in Cleveland, Ohio.
Impurities were determined by ICP-MS. Sulphur was determined by pyrohydrolysis followed by ion chromatography. Mercury was determined by cold vapour atomic absorption. Antimony was determined by difference, consistent with the basis used in ASTM B237 and standard industry practice.
Determination by difference means the antimony figure is calculated by subtracting measured impurities from the total rather than measured directly. That is the accepted basis under the specification, and it is worth understanding when reading the headline number.
ASTM B237, Standard Specification for Refined Antimony, sets the chemical requirements for refined antimony in ingot, pig or cake form in two grades. Grade A (UNS M00998) requires a minimum of 99.8% Sb. Grade B (UNS M00995) requires a minimum of 99.5% Sb.
Regulus II is a commercial grade of antimony metal requiring greater than 99.65% Sb. It is the grade most commonly referenced in physical antimony trade.
Sample S-260930-294 cleared both. The other four samples, at 99.5% to 99.6%, would meet ASTM Grade B but fall short of Regulus II and Grade A.
Washington: White House Critical Minerals Roundtable
AT4 Executive Director of Government Relations & Marketing, Andre Booyzen, was invited to join the World Trade Center Utah delegation to Washington D.C. for a series of roundtable meetings at the White House on 5 October 2026, hosted by the Office of the United States Trade Representative and the White House.
The stated objectives of the delegation were to connect Utah critical minerals producers with buyers and defence primes to advance offtake agreements, to connect projects with federal investors, and to identify the trade, permitting and financing actions that expand the United States industrial base for critical minerals.
Andre Booyzen, AT4 Executive Director of Government Relations & Marketing (far right), at the White House, Washington D.C., 5 October 2026, with members of the World Trade Center Utah delegation. Image: American Tungsten & Antimony Ltd.
Key people met with included:
The Company states that conversations at the roundtable meetings were focused on AT4 pursuing further funding and offtake arrangements with the United States government.
The presence of the Office of Strategic Capital in that list is notable. OSC runs the Department of War credit programs that have been expanded substantially and deployed into domestic critical minerals processing.
Members of Congress Visit White Spar and Del Sol
Members of Congress visited the White Spar Antimony Mine in Yavapai County, Arizona and the Del Sol Refinery in Amargosa Valley, Nevada on Tuesday 6 October and Thursday 8 October 2026.
The White Spar visit included Congressman Paul Gosar (Arizona), Chairman of the House Committee on Natural Resources Bruce Westerman (Arkansas) and Congressman Eli Crane (Arizona). Congressman Gosar subsequently visited the Del Sol Refinery.
Del Sol is a constructed and permitted hydrometallurgical antimony refinery using alkaline leach and electrowinning. The Company is separately assessing the addition of a tungsten ammonium paratungstate circuit at the facility, with Metso Finland Oy engaged on that concept study.
Craig Wiita, Del Sol Refinery CEO, and Andre Booyzen, AT4 Executive Director of Government Relations & Marketing, welcomed Congressman Paul Gosar to the Del Sol Refinery. Image: American Tungsten & Antimony Ltd.
What Spec-Grade Metal Unlocks
The Position
In under three months AT4 has moved from a federal shortlisting to assayed metal at the highest grade under ASTM B237. That is a faster progression than most developers manage, and the result is verifiable rather than asserted. One sample of Grade A ingot is a meaningful technical proof point and it is the thing that lets qualification conversations start.
What it is not is production. One sample of five reached 99.8%. The other four sat at 99.5% to 99.6%, which clears ASTM Grade B but not Regulus II or Grade A. The Company expects optimised electrowinning and fire refining to lift grades consistently above Regulus II, and that expectation has not yet been demonstrated across a campaign. No recovery, production rate or volume figures have been reported.
The corporate position also remains open. The acquisition of Nexus Metals Pty Ltd, which holds the rights to Del Sol and White Spar, has not completed, and AT4 does not currently own or control either asset. Everything described above has been achieved on assets the Company is still working to acquire.
This article is general information only. It is not financial product advice and does not take into account any person’s objectives, financial situation or needs. Images are reproduced from the Company’s ASX announcement dated 13 October 2026. Investors should read the Company’s ASX announcements in full, including those dated 28 July, 19 August, 21 August, 1 September, 4 September, 16 September, 21 September and 13 October 2026, together with the cautionary and forward-looking statements contained in them, and obtain independent advice before making any investment decision.
