Red Mountain Mining Ltd (ASX:RMX) Acquires Utah Antimony Project in World Class District!

11 September 2025

Price Sensitive Announcement $

Highlights:

• RMX has acquired 87 claims in the prospective Antimony Mining District in Utah, USA –
  Utah Antimony Project
• Red Mountain’s Utah Antimony Project directly adjoins Trigg Minerals’ (ASX: TMG)
  Antimony Canyon Project (ACP) – one of the largest and highest-grade Antimony projects in the USA, with a defined conceptual Exploration Target of 12.8 to 15.6 Mt @ 0.75% to 1.5% Sb, containing between 96,000 to 234,000 tonnes of Antimony metal1
• In the Antimony Mining District, Antimony mineralisation is mainly hosted within early
  Palaeocene sandstones and conglomerates of the Flagstaff Formation. The mineralisation is closely associated with north–south faults, which provide pathways for hydrothermal fluids
• Flagstaff Formation and controlling structures outcrop within TMG’s claims and are interpreted to extend under shallow cover (less than 20m) into RMX’s Utah Antimony Project
• The Trump administration has taken urgent measures towards securing its critical mineral supply chains with the intention for a federal investment up to US$1b, announced in August
• RMX’s exploration plan is to deploy geophysics to map prospective structures beneath the shallow cover, followed by sampling of basement on priority targets

Overview:

Red Mountain Mining Limited a Gold and Critical Minerals exploration and development company, is pleased to announce that it is has acquired the Utah Antimony Project (Figure 1) which consists of 87 claims, Located 11km east of the town of Antimony, Utah.

The Antimony Mining District was discovered in 1879 and produced high-grade Sb ores from multiple small-scale mines from 1880 to about 1908 and intermittently into the 1960’s2

Antimony mineralisation in the Antimony Mining District

RMX’s claims lie immediately along strike to the north and south of Trigg Minerals’ (ASX:TMG) Antimony Canyon Project (Figure 1). Trigg recently entered the district through the initial purchase of 49 mining claims (ASX: TMG Announcement 20 May 2025). ACP includes more than 30 small historical mine workings surrounding both Antimony Canyon and Drywash Canyon, approximately 6km north of the main prospect.

Antimony mineralisation within the Antimony Mining District is related to a north-south trending fault system interpreted to be splays of the Paunsaugunt Fault. These structures are considered to have acted as pathways for hydrothermal fluids sourced from nearby volcanic centres. Antimony is typically found in discrete veins or in stockwork zones, where numerous stibnite veins form dense networks within the host rocks that run roughly parallel to the surrounding rock layers.

At Antimony Canyon and Drywash Canyon, the main host unit is the Early Palaeocene Flagstaff Formation, comprising carbonate-rich fluvial sandstones and conglomerates. Recent work by Trigg Minerals3 (ASX: TMG) has highlighted a brittle felsic volcaniclastic horizon within the Formation as a particularly prospective host, with mineralisation also observed across multiple rock layers. This indicates potential that mineralisation extends both across the area and to depth. Channel sampling by TMG within and adjacent to historical workings has returned multiple assays exceeding 10% Sb, including a best result of 1.5 m @ 33.2% Sb from the Stebenite Mine at Antimony Canyon.

Antimony Canyon and Drywash Canyon represent two eroded windows into the Flagstaff Formation through a thin (interpreted to be mostly <20m thick), but laterally extensive blanket of alluvial and sedimentary cover. However, north-south trending faults that provide fluid conduits for antimony-rich mineralising fluids and the Flagstaff Formation host stratigraphy are interpreted to extend beneath the cover and into RMX’s tenements. RMX therefore believes that our Utah Antimony Project has high potential for discovery similar mineralisation to that seen at Antimony Canyon and Drywash Canyon.

Company Notes:

Red Mountain Managing Director, Lincoln Liu commented:
“The Utah Antimony Project is a compelling project, with which aligns with the US Government’s urgent push to secure its critical mineral supply chains by rapidly building domestic supply. Our project lies adjacent to Trigg Minerals’ Antimony Canyon Project, which is leading the way to become one of the first significant modern domestic producers of Antimony for the US market. The geological elements critical to Trigg’s high-grade mineralisation are thought to extend beneath shallow cover into our claims, so we are confident of making similar discoveries. With our established and highly experienced technical and US- based corporate team, RMX is in a tremendous position to rapidly advance our Utah Antimony Project.”