Antimony Ridge Metallurgy Advancing with Antimony Trioxide Produced

written by Raj Shah | April 14, 2026

Successful Testing Progressing with Conventional Pyrometallurgy and Hydrometallurgy Processing Options

April 14, 2026 (Source) — HIGHLIGHTS

  • Antimony Trioxide Produced: Antimony trioxide product has been produced from large samples of stibnite from the Antimony Ridge historical open pits, using the conventional pyrometallurgical process of volatilisation, producing an intermediate product, with 99.38 wt% Antimony Trioxide (Sb2O3wt%) content.
  • Further Antimony Trioxide Refining Test Work: Further refining pyrometallurgical test work is underway and final product results will be released in the coming weeks.
  • Conventional Pyrometallurgy: Pyrometallurgy would be the base-case, conventional technology for processing antimony, with initial tests conducted by KPM in Ontario to produce antimony trioxide. A number of third parties have been approached regarding this processing option.
  • Mineral Processing Test Work Progressing: Test work is advancing on Antimony-bearing stibnite veins, that have returned exceptionally high-grade Antimony (Sb) consistently above 30% up to 50% Sb in recent results, mined historically during World War I &II and the Korean War, from Antimony Ridge, within Resolution’s Horse Heaven Antimony-Tungsten-Gold-Silver Project (“Horse Heaven”) (ASX announcement 15 September 2025).
  • Concentrate Test Work: Test work is advancing on options to concentrate the antimony ore, tungsten and gold at IMO labs in Perth, Australia.
  • Hydrometallurgy Progressing: Test work on Antimony Ridge samples using hydrometallurgical processing is underway at ANSTO in Australia and results will be released once available.
  • Current Lack of US Processing Options: Resolution’s goal is to develop a hydrometallurgy processing hub for antimony, as stibnite, in Idaho USA, due to the lack of modern processing options in the USA for antimony.
  • Numerous Vein Swarms: 3D modelling of numerous known antimony and silver bearing veins, veins swarms and stockworks, over a large area (1,000m x 700m) (170 acres), has revealed significant size and expanding scale potential at Antimony Ridge (ASX announcement 10 April 2026).
  • FAST-41: Horse Heaven wasselected for the U.S. FAST-41 Transparency Coverage by the US-based Permitting Council, expected to accelerate permitting timelines with an application for 250 drill holes and large-scale bulk sampling (ASX announcement 8 April 2026).
  • Antimony Ridge forms part of Resolution’s broader Horse Heaven strategy, which includes recently acquired processing infrastructure, tungsten stockpiles and a major 2026 drilling program at Golden Gate starting in May.

Resolution Minerals Ltd (ASX: RML; OTCQB: RLMLF) (“Resolution” or the “Company”) is pleased to report that an intermediate antimony trioxide product has been produced from large samples of stibnite from the Antimony Ridge open pits, by the respected lab, Kingston Process Metallurgy (KPM), in Ontario.

Metallurgy test work is advancing on antimony-bearing stibnite veins, that have returned exceptionally high-grade antimony (Sb) consistently above 30% up to 50% Sb in recent results.

Conventional pyrometallurgy test work would provide the base-case data for processing antimony, with initial tests conducted by KPM in Ontario to produce antimony trioxide as an intermediate product. Final product results will be released in coming weeks. A number of third parties have been approached
regarding this processing option.

Test work on Antimony Ridge samples using hydrometallurgical processing is underway at ANSTO in Australia and results will be released once available.

Test work is advancing on options to concentrate the antimony ore, tungsten ore and gold-bearing samples at IMO labs in Perth, Australia.

Resolution’s plan is to develop a hydrometallurgy processing hub for antimony, as stibnite, in Idaho USA, due to the lack of modern processing options in the USA for antimony.

Adam Roper, PhD, Resolution’s In-house Senior Metallurgist, stated: “The initial pyrometallurgical results from processing Antimony Ridge samples are very encouraging with few impurities. This is a great start and I’m looking forward to discussing the final results in the coming weeks.

“Resolution’s goal is to develop a processing hub in Idaho for stibnite and I’m relishing the opportunity to bring this to fruition, from mine to product.
“The Johnson Creek Mill site, at the base of Antimony Ridge, is being considered as a fast track option for potential development of a local processing site, given it has the necessary infrastructure on site, with power and water, and is on 10 acres of private land owned 100% by RML.”

Ari Zaetz, RML’s Managing Director, stated: “With the recent US Government Permitting Council provided via FAST-41 Coverage to accelerate permits, Resolution is in parallel developing further local processing plans to enable antimony and tungsten supply for US demand. Our unique combination of critical minerals assets makes us well placed to deliver.”

Results of recent 3D modelling of the numerous antimony and silver-bearing veins and vein swarms that are exposed over a large area (1,000m x 700m) in past mining pits, reveals the potential for a significant size antimony-silver deposit at Antimony Ridge, with an open-ended target and expanding scale potential.

This result follows the selection of Antimony Ridge for FAST-41 Transparency Coverage from the US Permitting Council, announced on 8 April 2026. Selection reflects the strategic importance of Antimony Ridge as a potential source of U.S. domestic antimony supply, a critical metal essential for defence, energy, and industrial applications.

Historical mining occurred at Antimony Ridge by the US Government during World War I, WWII and the Korean War. During World War II, the local District, including the adjoining Stibnite mine (Perpetua Resources), is estimated to have produced more than 90% of the US Antimony (Source: Perpetua Resources Stibnite Feasibility Study, Jan 2021). Antimony Ridge was a key source of Antimony for the US military. Antimony Ridge is located within Resolution’s Horse Heaven Antimony-Tungsten-Gold-Silver Project in Idaho, USA, and immediately adjacent to Perpetua Resources’ Stibnite Gold Project, a large, recently permitted Antimony-Gold project.

Figure 1: Antimony Ridge – As part of Resolution’s larger Horse Heaven Antimony-Tungsten-Gold-Silver Project – Relationship of Antimony Ridge (Sb) with Golden Gate (Au) and Golden Gate Tungsten (W).

Future Plans

Resolution plans to commence a significant bulk sampling program of high-grade antimony ore and conduct an extensive drilling program up to 250 drill holes, once a Plan of Operations is approved (ASX announcement 8 April 2026). Antimony trioxide product has been produced from large samples of stibnite from the Antimony Ridge historical open pits. Further refining pyrometallurgical test work is underway and final product results will be released in the coming weeks. Antimony Ridge is expected to be a cornerstone of Resolution’sstrategy to supply critical metals, including Antimony, Tungsten and Gold, from central Idaho in the USA.

Resolution is initiating a major Phase 2 drilling program in May 2026, at the Golden Gate Project, of up to 45,000 ft (13,700 metres) of diamond core drilling located within the Company’s larger Horse Heaven Antimony-Tungsten-Gold-Silver Project. The program is designed to define the scale of gold and tungsten mineralisation at Golden Gate and Golden Gate South and support progression toward a maiden Mineral Resource Estimate.

Figure 2: Antimony Ridge – Past open pits and trenches from WWI & II and Korean War, with access roads, in 3D satellite image looking NE.

For further information, please contact:
Aharon Zaetz
Executive Director
Resolution Minerals Ltd
M: +61 424 743 098
[email protected]

Jane Morgan
Investor Relations
Jane Morgan Management
M: +61 405 555 618
[email protected]

Forward Looking Statements

This announcement may contain forward-looking statements. These statements relate to the Company’s expectations, beliefs, intentions or strategies regarding the future. These statements can be identified by the use of words like “anticipate”, “believe”, “intend”, “estimate”, “expect”, “may”, “plan”, “project”, “will”, “should”, “seek” and similar words or expressions containing same. These forward-looking statements reflect the Company’s views and assumptions with respect to future events as of the date of this release and are subject to a variety of unpredictable risks, uncertainties, and other unknowns. Actual and future results and trends could differ materially from those set forth in such statements due to various factors, many of which are beyond our ability to control or predict. These include, but are not limited to, risks or uncertainties associated with the acquisition and divestment of projects, joint venture and other contractual risks, metal prices, exploration, development and operating risks, competition, production risks, sovereign risks, regulatory risks including environmental regulation and liability and potential title disputes, availability and terms of capital and general economic and business conditions.

Given these uncertainties, no one should place undue reliance on any forward-looking statements attributable to the Company, or any of its affiliates or persons acting on its behalf. Subject to any continuing obligations under applicable law, the Company disclaims any obligation or undertaking to disseminate any updates or revisions to any forward-looking statements in this announcement to reflect any change in expectations in relation to any forward-looking statements or any change in events, conditions or circumstances on which any such statement is based.

Competent Person’s Statement

The information in this report that relates to exploration results, is based on and fairly represents information reviewed and compiled by Mr Ross Brown BSc (Hons), M AusIMM, Principal Geologist/director of exploration consulting firm, Riviere Minerals Pty. Ltd, who is a Member of the Australasian Institute of Mining and Metallurgy. Mr Brown has sufficient experience, which is relevant to the exploration activities, style of mineralisation and types of deposits under consideration, and to the activity which has been undertaken, to qualify as a Competent Person as defined in the 2012 Edition of the “Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves”. Riviere Minerals is consulting to Resolutions Minerals Limited and consents to the inclusion in this announcement of the matters based on their information in the form and context in which it appears.

The Company confirms it is not aware of any new information or data that materially affects the information cross referenced in this announcement and further to “Agreement to Acquire Major US Antimony Project and Placement” on 11 June 2025, “Exceptional Rock Chip and Soil Results from Antimony Ridge” on 15 September 2025, “Exceptional Rock Chip and Soil Results Update” on 24 September 2025, “Significant Gold Discovery at Horse Heaven Project” on 28 October 2025, “Significant Gold Discoveries Continue at Golden Gate” on 3 November 2025, “Golden Gate Discovery Grows with Multiple Gold Intercepts” on 2 December 2025, “Further Ultra High Grade Antimony and Silver Results” on 14 January 2026, “New Gold Discovery at Golden Gate South” on 9 February 2026, “Gold & Significant Tungsten Mineralisation in Drilling” on 17 February 2026,“Exceptional Tungsten Grade Identified in Stockpile Material” on 26 March 2026 and “Antimony Ridge Model Shows Extensive Vein Swarms” on 10 April 2026. The Company confirms that the form and context in which the Competent Person’s findings are presented have not been materially modified from the original announcements.

About Rivere Minerals

Riviere Minerals Pty Ltd (“Riviere”) is a resource consultancy specialising in project evaluation and portfolio management. Its principal geologist and sole director, Mr Ross Brown, has nearly 40 years of experience in mineral exploration worldwide.

Through Riviere, Mr Brown also provides assistance in exploration planning, execution and ASX reporting.