Highlights

  • Red Mountain Mining produced a 51.8% antimony concentrate at Oaky Creek with 85% metal recovery.
  • Metallurgical testing confirmed low deleterious elements and strong stibnite-dominated mineralisation.
  • ASX: RMX shares rose around 3–7% as investors reacted to high-grade critical minerals results.

Shares of Red Mountain Mining Limited (ASX:RMX) attracted investor attention following the release of metallurgical test results from its Oaky Creek Antimony Prospect in New South Wales. The company reported production of a high-quality 51.8% antimony concentrate with an 85% Recovery Rate, a result that positions the project as a potentially significant contributor within Australia’s emerging critical minerals sector.

The stock rose around 3.45% to 0.060 AUD, extending its strong annual performance as investors responded to improved confidence in the project’s metallurgical viability and scale potential.

Share Performance Reflects Growing Critical Minerals Interest

Red Mountain Mining’s share price movement reflects broader investor enthusiasm for antimony and critical minerals exposure within the Australian exploration sector. Antimony has gained strategic importance due to its use in flame retardants, alloys, and emerging energy storage applications, contributing to increased market attention on new Supply sources.

The latest announcement provided a key technical milestone rather than a resource update, but markets often respond strongly to metallurgical breakthroughs in early-stage projects. The ability to produce a high-grade concentrate with strong recovery rates is typically viewed as an important validation step before resource definition drilling.

Investor sentiment has also been supported by the scale of the broader Oaky Creek system, which the company believes spans approximately 3 kilometres of strike and includes multiple drill-ready targets.

Metallurgical Results Confirm High-Quality Antimony Concentrate

The central focus of the announcement was the successful production of a high-grade antimony concentrate from a representative bulk sample collected at surface historical workings. The sample, derived from stibnite vein material, returned a head grade of approximately 19.9% antimony (Sb), with rock chip samples from the area reaching up to 39.3% Sb.

Through a pilot crush, grind, and flotation program conducted by Auralia Metallurgy, the material produced a concentrate grading 51.8% Sb. This exceeds typical commercial concentrate grades of 30–40%, indicating strong potential product quality if scaled.

The flotation process achieved an 85% recovery of antimony, a level generally considered highly favourable in early-stage metallurgical testing. Recovery rates of this magnitude suggest that a significant proportion of contained metal can be economically extracted under optimised processing conditions.

The concentrate also contained low levels of deleterious elements such as arsenic, which was below detection in the head sample and measured at low levels in the final concentrate. This is particularly important in antimony processing, where impurity levels can influence Downstream smelting costs and product marketability.

Mineralogy Supports Simple Processing Pathway

Detailed mineralogical analysis showed that the sample is dominated by quartz (approximately 50.5%) and stibnite (about 25.2%), with minor clay, carbonate, and iron-bearing minerals. The dominance of stibnite is significant, as it is the primary antimony-bearing mineral and is generally amenable to flotation-based processing.

X-ray diffraction and TIMA analysis confirmed that antimony occurs primarily in stibnite, with limited presence of secondary oxidised minerals. This simplifies metallurgical interpretation and supports the effectiveness of conventional flotation techniques used in the test program.

The coarse grind size (P80 of 212 microns) and relatively short flotation time of 14 minutes further highlight the efficiency of the process under laboratory conditions. These parameters are often used as early indicators of potential processing simplicity, though they require validation at scale.

Oaky Creek Emerging as a Significant Antimony System

Beyond metallurgy, the Oaky Creek prospect itself is emerging as a potentially large-scale orogenic antimony system. The company has identified a mineralised strike length of approximately 3 kilometres, with multiple zones of elevated antimony in soil and rock chip sampling.

Previous exploration has returned high-grade surface results exceeding 25% Sb across multiple locations, reinforcing the interpretation of a continuous mineralised system rather than isolated occurrences.

Soil geochemistry has outlined coherent anomalies extending north and south of historical workings, while infill sampling has further refined at least five high-priority drill targets scheduled for testing in 2026.

The geological setting within the Southern New England Orogen is also significant. The region is recognised as Australia’s premier antimony province, hosting several notable deposits including the nearby Hillgrove system operated by Larvotto Resources Limited.

Geological Setting and Exploration Upside

The Oaky Creek mineralisation occurs within quartz-carbonate-stibnite veins and breccias hosted in folded Carboniferous metasediments. This structural setting is typical of orogenic antimony systems, which often form along major fault zones.

The project lies within the broader Armidale Antimony-Gold Project, which spans approximately 85 kilometres along the Peel Fault system. This regional-scale structure is considered highly prospective for orogenic gold and antimony mineralisation but remains relatively underexplored.

The company’s interpretation of soil and rock geochemistry suggests a coherent mineral system with multiple zones of anomalism aligned along structural corridors. This supports the potential for further discovery beyond currently defined targets.

Exploration and Development Pathway

The company is now preparing for drilling activities at Oaky Creek, with five high-priority targets identified for testing. These targets have been defined through integrated soil sampling, rock chip data, and geological interpretation.

The upcoming drilling program will be critical in determining the depth continuity of mineralisation and validating whether surface-grade antimony extends into economically significant underground systems.

In parallel, the company is also advancing Due Diligence on its Pioneer Tungsten Project in the United States, indicating a broader strategic focus on critical minerals across multiple jurisdictions.

Conclusion

Red Mountain Mining’s latest metallurgical results represent a significant technical milestone for the Oaky Creek Antimony Prospect, demonstrating the ability to produce a high-grade concentrate with strong recovery and low impurity levels. Combined with extensive surface geochemistry and a large-scale structural setting, the project is emerging as a potentially important antimony system within Australia’s critical minerals landscape. While exploration and drilling remain essential next steps, the latest results have strengthened investor confidence in the technical viability of the asset and contributed to renewed momentum in ASX: RMX.