Six antimony routes, and the defence specification only one has cleared

Six companies are building routes to antimony for the United States. The document a defence-grade product must satisfy dates from 1972 and has been inactive for new design since 2014.

Each of the six can be placed at the stage it is actually at, on its own filings. Placed that way, only one has cleared the specification a primer line works to, and it did so from Mexican ore.

On 21 September 2026 American Tungsten and Antimony announced a metal ingot poured in Nevada, and it was reported as a mine-to-metal breakthrough. The company stated in the same document, in terms, that it holds no legal or beneficial interest in either the refinery that made the ingot or the mine that supplied the ore, and that it was not reporting the grade, purity or metallurgical recovery of the material while independent testing continues. What it has agreed to buy is not the assets but a company holding option and earn-in rights over them, and completion remained conditional on a shareholder vote held that day, on exercise of the refinery option and on regulatory and third-party consents. All of that is in the filing. None of it is in most of the coverage.

That gap, between what a company discloses and what the market hears, is a compelling reason to do this exercise once a quarter rather than once a year. Six named routes to new antimony supply for the United States have published enough to be placed on the chain. Placed there, the chain is crowded at the start and almost desolate at the end.

Antimony reaches the armed forces in several forms, from the antimony-hardened lead in bullet cores and the antimony trioxide that makes textiles and plastics flame retardant to the indium antimonide in infrared detectors. All of them matter. This article follows one: antimony trisulfide, the primer compound, and the specification it has to meet.

Start with the document at the end of the chain, because it has not been named in this publication before but will be instrumental moving forward in the defence allocation of our coverage. The military specification for antimony sulfide in ammunition is MIL-A-159D (AR), dated May 1972, prepared by the Army armaments activity, with review by two further Army activities and the Defense Logistics Agency. It covers two types and five classes of antimony sulfide. Notice 1 of 14 July 1999 reviewed it and found it valid for use in acquisition. Its current status is inactive for new design, under Notice 2 dated 15 May 2014, which superseded Notice 1. The notice text is unambiguous: the specification is inactive for new design and is no longer used, except for replacement purposes. No revision or replacement has been published since, and antimony sits outside the defence sourcing restrictions Congress has extended to tungsten, tantalum, gallium and germanium.

‘Inactive for new design’ could easily be misread as cancellation. It is not. Replacement purposes covers what primer stock is: an item in continuous production against an existing design. On the only published precedent, the specification remains the document a new source would have to satisfy, and its being inactive for new design means only that no new item will be designed around it. A new supplier entering this market is therefore entering against a document written in 1972, never revised since, and inactive since 2014.

What the pathway looks like in practice is on the record once, in United States Antimony’s own filing with the Securities and Exchange Commission rather than a press release. In September 2019 a Defense Logistics Agency award of $510,528, described in the filing as a grant and as a firm fixed price contract, with a period of performance of one year, funded a domestic antimony trisulfide source qualification for the National Defense Stockpile. The sequence as filed was sample selection and testing from the company’s mine in Mexico, six batches of trisulfide produced, block material shipped to a third party for grinding, sizing, packaging and quality control, participation in an integrated product team with the agency and the Army, and iteration against testing feedback across subsequent lots, to a target specification named in the filing as MIL-A-159D, Class 1, Type 1. That is what qualification is. It is lots, feedback and iteration against a chemical specification, and it took United States Antimony from award to a stated third and final sample approval in roughly three and a half years. It was run for the stockpile rather than for a primer line, but it remains the only published record of the sequence.

United States Antimony remains the only one of the six to have completed that sequence, with a third and final sample approval announced in March 2023, from Mexican concentrate rather than domestic ore. Its current defence business is different in kind: a five-year sole-source contract with a ceiling of up to $245m for metallic antimony in ingot form for the National Defense Stockpile, against which approximately 82,000 pounds had been accepted by July 2026, the latest acceptance it has disclosed. Ingot is not trisulfide and the company has never claimed otherwise. It has the qualification and the contract, but for different products.

Against that, the other five.

Perpetua Resources is the furthest along of the new entrants, and the only one whose pathway the customer has described in its own publications. The Defense Ordnance Technology Consortium effort, contracted through Army Contracting Command New Jersey under an Ordnance Technology Initiative Agreement, was put at $22.4m by the Army in September 2025, and the company’s quarterly report now gives a current estimated amount of $27.1m. The period of performance was extended through the end of 2026 in May 2025; the company has published no end date since a further award in June 2026. A military-grade antimony sulfide processing facility prototype opened at Idaho National Laboratory on 29 July 2026, and the Army says it will continue processing capability demonstrations until raw antimony sulfide production begins at the Stibnite mine, scheduled for late 2028. Separately, a Defense Production Act Title III agreement of $59.2m funded permitting and construction readiness at the mine; it expired in June 2025 with all funds disbursed. Financing is approved and not closed: the Export-Import Bank board unanimously approved a $2.9bn senior secured facility on 21 May 2026, being $2.4bn upfront plus capitalised interest during construction and the exposure fee, over 13 years with repayments anticipated from 2030, and the quarterly report filed on 14 August 2026 records that definitive documentation has not completed and that the terms or amount may differ. For now it is a prototype, running against a period of performance whose last published end date is December.

Nova Minerals, through Alaska Range Resources, holds a $43.4m Department of War Title III award announced on 1 October 2025 to extract, concentrate and refine stibnite-bearing material to military-grade antimony trisulfide, with approximately 500 tons of processing and refining equipment landed at Port MacKenzie on 6 September 2026 and first trisulfide targeted for 2027. No period of performance and no qualification milestone has been published. It is at the mine development stage: the Stibium mine plan awaits state approval and the refinery is still being built.

American Tungsten and Antimony has an ingot and, on its own disclosure, no interest in the plant that made it. The ASX announcement lodged on 21 September 2026 records antimony ingot produced at the Del Sol Hydromet Refinery in Nevada from White Spar mine ore in Arizona, states expressly that the company has no legal or beneficial interest in either, and does not report grade, purity or metallurgical recovery while independent testing continues. What the company has agreed to buy is Nexus Metals, which holds option and earn-in rights over both assets. Shareholders approved the acquisition the same day, with every resolution carried on at least 95 per cent of votes cast, and at the time of writing no completion notice has been lodged. The company is also negotiating, and has not executed, a Department of Energy selection of up to $18m for antimony smelting capacity, the allocation of which it says may extend to Del Sol. The product is metal. The announcement names trisulfide only as a downstream product the ingot could feed, and says samples will now go into customer qualification; it gives no specification and no qualification timeline. What it is running is a demonstration campaign at a plant it does not own and whose purchase option has not yet been exercised.

Larvotto Resources has concentrate and no named military primer route beyond it. First concentrate was produced at Hillgrove in New South Wales on 21 September 2026, with the announcement stating approximately 4,900 tonnes of antimony and 40,500 ounces of gold a year over an initial eight-year mine life. Antimony concentrate at a 60 per cent product specification is covered by a binding offtake with the trader Wogen Resources, completed in December 2024, under which Wogen holds exclusive global sales rights for the first seven years; gold concentrate goes to Glencore International AG. No smelter is named anywhere in the document. Concentrate at 60 per cent marketed through a trader has no disclosed destination and no disclosed end product. United States Antimony bought about 10 per cent of Larvotto in October 2025 and made a takeover proposal that Larvotto’s board rejected. It is in production, but of a concentrate that sits upstream of the primer qualification pathway, with no disclosed route into it.

Korea Zinc completes the six. Its Onsan smelter in South Korea already recovers antimony, but the company discloses no volume for it. Its own investor material of January 2026 states planned antimony production of 2,559 tonnes a year at a planned Clarksville, Tennessee facility targeting trial operations in 2029, described as approximately 10.8 per cent of United States market demand of 24,000 tonnes, a figure it attributes to the USGS. A widely repeated figure of approximately 10 tonnes a day at Onsan comes from an interview with the smelter’s head, not from a disclosure, and what United States import detail shows is examined separately in this batch. It is recovering antimony in Korea and planning a plant in Tennessee.

Set out this way the six do not divide into leaders and laggards. They divide by what they have. One has material and no route to the compound. Two have a route to the compound and no material at commercial scale. One has an ingot from a plant it does not yet own. One has a qualification for trisulfide and a contract for ingot. One has an operating smelter abroad and a plant planned in Tennessee.

Only United States Antimony has an approval on the record: its target specification in 2019 and its final sample approval in 2023, from Mexican material. None of the five new entrants has yet stated a lot accepted against MIL-A-159D, and none has published a specification number, a sample submission, an assay against a trace element limit, or a date on which a lot passed. Perpetua comes closest, and what its customer has published is a prototype facility conducting capability demonstrations, against a period of performance whose last published end date is December. A Perpetua announcement of Army funding describes antimony trisulfide as an essential and non-replaceable component of over 300 types of munitions, and Army public affairs has put antimony sulfide in nearly 30 per cent of military ammunition items.

The Army organisation running the programme has also changed its name, which makes coverage harder to follow. JPEO Armaments and Ammunition was folded in February 2026 into the Capability Program Executive for Ammunition and Energetics, under a new Portfolio Acquisition Executive for Agile Sustainment and Ammunition activated at Picatinny Arsenal under Major General John Reim. Anyone searching the old name for a qualification announcement will find an organisation that no longer issues them.

The useful way to keep track of each company’s progress is not to ask who has announced capacity. All six have. For the five new entrants, it is to ask which first publishes a lot number, a specification number and a date. On the only documented precedent, that took United States Antimony, with an operating furnace and a government award, three and a half years. For United States Antimony, the question is whether a trisulfide contract follows the ingot one.