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RED MOUNTAIN MINING LIMITED
Symbol	RMXFF
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Red Mountain Mining Limited (RMXFF) Exceptional Oaky Creek Metallurgy Produces High-Grade 51.8% Antimony Concentrate with 85% Recovery

2026-05-24 18:35 ET - News Release

Perth, Australia, May 25, 2026 - (ABN Newswire) - Red Mountain Mining Limited (ASX:RMX) (OTCMKTS:RMXFF) a Critical Minerals exploration and development company with an established portfolio in Tier-1 Mining Districts in the United States and Australia, announced the results of geochemistry, detailed mineralogical characterisation and a pilot crush, grind and flotation study of a representative bulk sample of quartz-stibnite-carbonate vein material from the high-grade Oaky Creek Antimony prospect in the northern portion of the Company's 100% owned Armidale Antimony-Gold project in the Southern New England Orogen of New South Wales.

HIGHLIGHTS:

- Geochemical and detailed mineralogical characterisation and a pilot crush, grind and flotation study of a representative bulk sample of stibnite vein material from the high-grade Oaky Creek Antimony prospect has produced a high-quality concentrate at 51.8%, well above the 30-40% commercial grade, that would be an excellent feed stock for pyrometallurgical processing to produce a saleable Sb metal. The commercial concentrate produced a very high 85% antimony recovery

- The ~20kg sample was collected from shallow historical surface pits at Oaky Creek North and is broadly representative of the orogenic antimony mineralisation exposed at surface at Oaky Creek, the depth extent of which will be tested by the upcoming drilling program

- The bulk sample had a measured head grade 19.9% Sb and 0.25ppm Au, which is well within the range of mineralised rock chip grab samples from the Oaky Creek prospect, which have returned values of up to 39.3% Sb and 1.09ppm Au. Significantly, the sample returned a below detection result of <0.01% As, suggesting that Arsenic is likely in very low concentrations at Oaky Creek

- Mineralogically, TIMA analysis demonstrates that the sample is dominated by quartz (50.5%) with stibnite (25.2%) the next most abundant phase. Oxidised stibnite and Sb (Fe) oxyhydroxides collectively comprise 5.08%, with significant gangue phases including clays (6.41%), ankerite-dolomite (3.04%), calcite (2.66%), feldspars (2.48%), Fe oxides and hydroxides (2.02%), and chlorite (1.43%). Other sulfide and telluride phase are rare, totaling only 0.05%

- Based on the mineralogy, a coarse (P80 = 212um) crush was successfully trialed, with a total flotation time of fourteen minutes producing a composite concentrate of 51.8% Sb at a 29.7% mass pull, with an 85% recovery of the metal relative to head grade - Five priority targets which will be tested at the upcoming drilling program at Oaky Creek

- Red Mountain advises that Due Diligence activities at the Pioneer Tungsten Project in the United States are progressing well and on schedule, as part of the Company's option agreement over the Pioneer Tungsten Project

The ~20kg sample (Figure 1*) was collected from shallow historical surface pits at Oaky Creek North (Figure 2*) and is broadly representative of the orogenic antimony mineralisation exposed at surface at Oaky Creek, the depth extent of which will be tested by an RC drilling program that has been recently approved by the NSW Regulator.

Analysis of the bulk sample was completed by ALS Metallurgy (Table 2*) and returned a measured head grade of 19.9% Sb and 0.25ppm Au, which is well within the range of mineralised rock chip grab samples from the Oaky Creek prospect, which have returned values of up to 39.3% Sb and 1.09ppm Au. Significantly, the sample returned a below detection result of <0.01% As, suggesting that this deleterious element is present in very low concentrations at Oaky Creek.

etailed mineralogy confirms that almost all antimony occurs in stibnite A portion of the bulk sample was crushed and two size fractions (+212um and -212um) were submitted for Tescan Integrated Mineral Analyzer (TIMA) analysis, while the head sample was submitted for semi-quantitative X-ray diffraction (XRD) analysis. The XRD analysis of the head sample indicated that 59% of the sample comprised quartz, with 21% stibnite (Sb2S3), 1% stibiconite (Sb3O6(OH)) and <1% senarmontite (Sb2O3). Other significant gangue minerals included 10% clay minerals and 7% carbonate. No other sulfide phases were detected by XRD.

The TIMA analytical results on the crushed samples are summarised in Table 3. As can be seen, quartz is more abundant in the coarser (+212um) fraction, while the other minerals are more concentrated in the -212um fraction. Overall, quartz (50.5%) is the dominant mineral phase in the sample with stibnite (25.2%) the next most abundant phase. Oxidised stibnite and Sb (Fe) oxyhydroxides collectively comprise 5.08%, with significant gangue phases including clays (6.41%), ankerite-dolomite (3.04%), calcite (2.66%), feldspars (2.48%), Fe oxides and hydroxides (2.02%), and chlorite (1.43%). Other sulfide and telluride phase are rare, totaling only 0.05%, which is consistent with the below detection limit assay results for As, Cu, Pb and Zn (Table 2*).

Flotation study delivers a high-quality saleable antimony concentrate

Flotation testing was undertaken at Auralia Metallurgy, who used their Basil Latino flotation machine with a grind of P80 = 212um, a lead nitrate activator, potassium aryl xanthate (PAX) collecting agent and a glycol ether based H57 frothing agent. These reagents are typically used for sulfide ores of this type.

Five concentrates were produced from the flotation process, with individual flotation times varying from 1 to 8 minutes and a total flotation time of fourteen minutes producing a composite concentrate (Figure 3*) of 51.8% Sb at a 29.7% mass pull, with an 85% recovery of the metal relative to the head grade. The concentrate contained only 0.07ppm Au, with a much lower recovery of 32.8%, indicating that this metal is likely to be locked in solid solution. Importantly, and consistent with the head grade, the concentrate contained only 197ppm As, which is a low concentration of this deleterious element. The concentrate would be an excellent feed stock for pyrometallurgical processing to produce a saleable Sb metal, highlighting the potential quality of the antimony mineralisation at Oaky Creek, if a sufficient resource is defined by Red Mountain's planned drilling program.

Oaky Creek represents a significant 3km long orogenic antimony system with multiple drill ready targets

The Oaky Creek prospect features quartz-carbonate-stibnite veins and breccias hosted within a tightly folded and faulted sequence of metamorphosed Carboniferous mudstone, siltstone and fine sandstone. The mineralisation has been targeted by two groups of shallow historical pits and shafts at Oaky Creek North and Oaky Creek South.

The Company's initial sampling program at Oaky Creek comprised a 50m x 100m spaced grid soil sampling program centered on a major splay of the Namoi Fault, accompanied by rock chip sampling. As initially reported in June 2025, the soil sampling defines a coherent, ~1.5km long, 100-200m wide, NNW-trending >2ppm Sb in soil anomaly extending both north and south of the historical workings at Oaky Creek North and a similarly-oriented ~1km long >2ppm Sb in soil anomaly extending north from the Oaky Creek South workings.

Sampling campaigns at Oaky Creek, returned multiple rock chip samples with values of over 25% Sb and 0.1g.t Au for five different areas, with mineralised and anomalous rock samples showing a strong spatial correlation to the antimony soil anomaly (Figure 2*). When considered collectively, the soil and rock chip results indicate a significant orogenic antimony mineral system with a strike extent of 3km, which is analogous to Larvotto Resources' (ASX:LRV) (Market Cap. ~AU$610 million) Hillgrove Project, which lies east of Red Mountain's project area.

Red Mountain's ~1300 sample infill hand auger soil sampling campaign across the full ~3km strike extent of the Oaky Creek prospect was completed across the past two quarters to tighten the Company's existing 100m x 50m spaced soil grid in order to better constrain individual high priority drill targets. This detailed systematic work has allowed the company to define five high priority orogenic antimony targets for drill testing at Oaky Creek (Figure 2*) during the second quarter of 2026.

*To view tables and figures, please visit:
https://investorhub.redmountainmining.com.au/announcements/7551891

Red Mountain Mining Limited Announcements page:
https://investorhub.redmountainmining.com.au/announcements

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