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RED MOUNTAIN MINING LIMITED
Symbol	RMXFF
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Red Mountain Mining Limited (RMXFF) Delivers Major Increase in Yellow Pine Antimony

2025-11-20 17:32 ET - News Release

Perth, Australia, Nov 21, 2025 - (ABN Newswire) - Red Mountain Mining Limited (ASX:RMX) (OTCMKTS:RMXFF), an Australia and United States based Critical Minerals exploration and development company with an established and growing portfolio in Tier-1 Mining Districts, announced the expansion of its Yellow Pine Antimony Project within the Stibnite Mining District in Central Idaho, USA. Following a field mapping program in September immediately deployed after acquiring the project, the Company has now acquired additional claims, increasing its project size by 75%, immediately northeast of the initial project announced in September 20251 . This increases Red Mountain's footprint in this highly sought-after district to 426 hectares.

Red Mountain's Yellow Pine project is located less than 2km from Perpetua Resources' (NASDAQ:PPTA) (Market cap A$4.37 billion) Stibnite Gold-Antimony Project in central Idaho, USA and approximately 5km south of Resolution Minerals' (ASX:RML) (Market cap of approximately A$150 million) Horse Heaven Gold-Antimony project, which lies immediately west of Perpetua's claims (Figure 1*).

Strong results in the Yellow Pine Stibnite District highlight the exceptional prospectivity The Stibnite Mining District was a major source of antimony in the first half of the 20th Century.

Recorded production from the Yellow Pine and Hangar Flats deposits between 1932 and 1952 totalled 39,930 tonnes of Antimony. These two deposits and the West End Deposit, which produced gold and silver from 1978 to 1997, collectively comprise the Proven and Probable Reserve of 104 Mt @ 1.33g/t Au and 0.06% Sb for 4.8Moz Au and 148Mlbs Sb for Perpetua's Stibnite Project, which is the largest known stibnite deposit in the USA. Perpetua announced that they had broken ground on the early works construction for the Stibnite Project on October 21, 2025, following the placement of financial assurance and receipt of the signed Plan of Operations from the US Forestry Service; and also secured a total of US$333M (AU$513M) gross proceeds through a strategic equity investment of US$255M from Agnico Eagle and JPMorgan on October 28, 2025 and a registered equity offering of US$71M and concurrent US$7M private placement on October 30 and 31, 2025.

Immediately west of Perpetua's claims, Resolution Minerals has recently announced strong gold results from the first three holes drilled at their Golden Gate prospect. The three diamond holes returned exceptional broad intervals of gold mineralisation associated with the following results reported:

HH-GG25-001C: 189.2m @ 1.30 g/t Au from 34m, ending in mineralisation.
HH-GG25-002C: 265.2m @ 0.60 g/t Au from surface, ending in mineralisation.
HH-GG25-003C: 253.0m @ 1.50 g/t Au from surface, ending in mineralisation.

The mineralisation is open at depth, as well as in all directions and RML is currently undertaking additional diamond drilling. RML interpret the mineralisation at Golden Gate to be related to a large intrusion-related system, similar to the gold-stibnite mineralisation at the Stibnite deposit.

Exploration potential of RMX's Yellow Pine Antimony Project

2017 geological mapping by the Idaho Geological Survey shows that RMX's claims feature similar prospective geology to that seen within the Perpetua Resources' Stibnite Project area, with similar metasediments intruded by Idaho Batholith granite and cut by a major NNE-trending Tertiary fault and evidence of historical mining activity, most likely seeking gold and/or antimony (Figure 2*).

The expanded claim block secures the northeast continuation of the main fault as it moves into a key structural corridor within the metasediments, significantly strengthening Red Mountain's exploration position at the Yellow Pine Antimony Project and is expected to generate a series of new Antimony and Gold targets.

Field mapping by RMX's field crew has confirmed the presence of tectonic breccias within quartzite associated with the main NNE-trending fault (Figure 2*), indicating that hydrothermal fluid circulation occurred along the structure - a positive indicator for potential mineralisation. Red Mountain geologists have successfully located the two eastern historical workings mapped by the Idaho Geological Survey, which are small shallow pits targeting brecciated quartz veins prospective for gold and/or antimony (Figure 3*).

Yellow Pine Antimony Project Exploration Program

Red Mountain's further planned exploration program at Yellow Pine will map and sample the main NNE fault and the contact between the Idaho Batholith granites and the metasedimentary rocks. The aim is to confirm clear signs of fluid movement, broken mineralised rock and alteration that point to strong Antimony-Gold potential. These results will assist Red Mountain in defining high-quality drill targets.

Red Mountain set to continue aggressive US growth strategy

Red Mountain recently listed on the US stock market listing (OTCMKTS:RMXFF) to continue to aggressively seek further opportunities to expand its portfolio of high-quality Critical and Strategic Metals projects in Tier 1 US mining jurisdictions and gain US Capital markets support. In addition to Yellow Pine, the Company also holds high-quality antimony projects at Silver Dollar (Historic Antimony Mine) in Idaho and the Utah Antimony Project in the Antimony Mining District off Utah and is actively pursuing other opportunities with a goal of building a portfolio of assets to leverage what is an unprecedented critical shortage of Western supply and US Government interest in key strategic commodities.

Red Mountain's established and unique asset base is subject to ongoing discussions with potential US strategic partners to fast-track both its US and Australian Critical Minerals Portfolio. These discussions are focused on accelerating project development and leveraging partner expertise in navigating US Government funding programs and Critical Minerals project development and support.

*To view tables and figures, please visit:
https://abnnewswire.net/lnk/172228DD

About Red Mountain Mining Limited:

Red Mountain Mining Limited (ASX:RMX) is a mineral exploration and development company. Red Mountain has a portfolio of US, Canada and Australia projects in Critical Minerals and Gold. Red Mountain is advancing its Armidale Antimony-Gold Project in NSW, Utah Antimony Project in the Antimony Mining District of Utah, US, Fry Lake Gold Project and US Lithium projects.

Contact:

 
Mauro Piccini 
Company Secretary