Red Mountain Mining Limited (ASX:RMX) Silver Dollar Mine Area Reveals Strong Silver Prospectivity

Perth, Dec 11, 2025 AEST (ABN Newswire) - Red Mountain Mining Limited (ASX:RMX) (RMXFF:OTCMKTS), an Australian and United States based Critical Minerals exploration and development company with an established and growing portfolio of projects in Tier-1 Mining Districts, announced the results of a technical study at the Silver Dollar Antimony Project and adjacent area.

HIGHLIGHTS

- A technical study on the Silver Dollar Project in Idaho has highlighted the Silver and Gold potential of the locality with prospects identified immediately surrounding Red Mountain's claims reporting historical assays of up to 85.7 g/t Silver and 17.5 g/t Gold*

- Red Mountain's Silver Dollar Project features multiple Antimony, Silver and Gold mineral occurrences, including the previously mined "Silver Dollar Mine", a 10m deep shaft targeting a massive stibnite vein up to 1m thick

- Previous production from the Silver Dollar Mine has estimated average ore grades of 17.7% Antimony, including grade of 14.6% Antimony and 6.9 g/t Silver from a single sample (ASX 7 October 2025)

- RMX is set to commence its maiden exploration program at the Silver Dollar Project this week

- Red Mountain commissioned the study after acquiring the project in October, to identify high priority targets at the historic Silver Dollar Antimony mine:

o Additional new claims for expansion include the strong Silver & Gold prospects

o RMX intends to acquire the claims at the commencement of exploration program

- The stibnite vein mineralisation at the Silver Dollar Project is related to an ENE-striking, steeply N-dipping fault and the host rocks display an analogous geological setting to Perpetua Resources' (Nasdaq:PPTA) Stibnite Gold-Antimony Project (4.8Moz Au and 148 Mlbs Sb)

- Silver was recently added to the US Critical Minerals list and complements RMX's portfolio

- Silver prices have also surged higher, breaking new record highs above USD$60 per ounce

- Antimony price strength has been sustained, trading at USD$44,000 per tonne, coupled with the news of China's Antimony oxide export volumes falling sharply month-on-month in October (Source: metal.com 21/11/2025)

- The Company continues to assess projects in the Critical Minerals sector, with the mission of seeking to meet the urgent and unprecedented demand in the United States and the West for reliable and fast-tracked sources of Critical and Strategic Metals

The study highlights the Silver and Gold potential of the locality with prospects identified immediately surrounding Red Mountain's claims reporting strong historical assays of up to 85.7 g/t Silver and 17.5 g/t Gold. RMX's technical team intends to expand the Silver Dollar Project to include these highly prospective areas as the launch of the first-pass sampling program commences this week. The project is located southeast of both RMX's recently expanded Yellow Pine Antimony Project, and Perpetua Resources' Stibnite Gold-Antimony Project, which is the largest known antimony deposit in the USA, with a Proven and Probable Reserve of 104 Mt @ 1.33g/t Au and 0.06% Sb for 4.8Moz Au and 148Mlbs Sb.

RMX's Silver Dollar claims encompass four known alluvial gold-silver placers, the Kelly & Joe goldsilver prospect and two reported vein antimony mineral occurrences, including the Silver Dollar Mine (Figure 1*), which features a 10m deep shaft sunk into fractured granodiorite in 1944, targeting a massive stibnite vein up to 1m thick.

Gold and Silver - Precious metals Potential at Silver Dollar

As shown on Figure 1*, the area including and surrounding Red Mountain's Silver Dollar claims features multiple bedrock and alluvial silver and gold mineral occurrences, many of which feature historical pits and adits. The bedrock occurrences, which are named on Figure 1* and summarised in Table 1, are structurally controlled and associated with quartz veining and shear zones within the Idaho Batholith. Due to their narrow width, these dykes are not shown in the published USGS mapping shown in Figure 1*, but are clearly locally important in focusing hydrothermal fluid flow and as hosts for vein-style precious metal mineralisation.

Assay data for the bedrock precious metal occurrences shown in Figure 1* and listed in Table 1* are indicative of potential for high tenor mineralisation, with quartz vein samples returning best results of 6.9 g/t Au from Blind Ledge and 85.7 g/t Ag from Klondyke; and a selection of samples from Iron Crown with observed visible gold found to contain 17.5 g/t Au and 14.7 g/t Ag (Table 1*).

Red Mountain's field team will search for the presence of late dykes, veining and shearing within the Silver Dollar project area and sample any quartz veining or alteration that may host mineralisation.

Vein-style antimony mineralisation

As previously reported, the stibnite vein mineralisation at the Silver Dollar Mine, as well as that seen at the second, unnamed antimony mineral occurrence shown on Figure 1*, is spatially related and thought to be genetically linked to an ENE-striking, steeply N-dipping fault. The host rock at Silver Dollar is part of the Cretaceous Idaho Batholith, which is the same intrusive suite that hosts Perpetua Resources' Stibnite Project, where mineralisation is also structurally controlled, along early Tertiary north-south striking regional scale faults and smaller northeast-striking splays.

As reported by Choate (1962), the near-vertical, steeply north-dipping vein mined at Silver Dollar was "paper-thin" at surface, but at 25 feet (7.5m) depth it swelled to a width of three feet (~1m) and pieces of pure stibnite up to 45 pounds (20kg) in weight were removed during mining. The vein comprised a pure stibnite core with quartz gangue only at the margins. The shaft at Silver Dollar was sunk by Arthur McGowan, who recalled receiving $US56 per ton of ore shipped, which at a fixed US price of 15.84c per pound in 1944-1945, equates to a grade of 354lbs/ton, or 17.7% Sb. This value is consistent with the value of 14.6% Sb and 6.9 g/t Ag cited by the USGS for a sample from the Mine.

Both the Silver Dollar Mine and the unnamed antimony vein occurrence approximately 600m to the southwest are clearly structurally related to the NNE-striking fault that cuts Red Mountain's Silver Dollar Claims. This structure will be a focus for the Company's exploration team during this initial round of work.

Red Mountain set to continue aggressive US growth strategy

In November, Red Mountain secured a US stock market listing (RMXFF) to increase its capital markets exposure in the United States and to further align with its continued aggressive strategy to expand its portfolio of high-quality Critical and Strategic Metals projects in Tier 1 US mining jurisdictions. In addition to the Yellow Pine Antimony and Silver Dollar projects in Idaho, the Company also owns the Utah Antimony Project in the Antimony Mining District in Utah.

Following a successful funding initiative earlier this month, which was again supported by several investors who have featured as Top 20 shareholders of Larvotto Resources (ASX:LRV), Red Mountain is actively pursuing 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.

*To view tables and figures, please visit:
https://abnnewswire.net/lnk/6Z62R6JG


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