Red Mountain Mining Oaky Creek Antimony Delivers 51.8% Concentrate Grade

Red Mountain Mining Delivers Standout Metallurgy at Oaky Creek — 51.8% Antimony Concentrate with 85% Recovery Sets the Stage for Drilling

Red Mountain Mining Oaky Creek antimony metallurgy results have captured significant attention following the company's latest announcement. Red Mountain Mining (ASX: RMX) has revealed a major metallurgical breakthrough at its Oaky Creek Antimony prospect within the 100%-owned Armidale Antimony-Gold Project in New South Wales. A pilot crush, grind, and flotation study on a representative bulk sample of high-grade stibnite vein material has produced a concentrate grading 51.8% antimony (Sb) — well above the 30–40% commercial benchmark — at an impressive 85% metal recovery.

The result positions Oaky Creek as a genuinely high-quality antimony system, and comes just ahead of a planned RC drilling programme that will test the depth extent of mineralisation across five defined priority targets.

What the Metallurgical Results Tell Us

The ~20kg bulk sample was collected from shallow historical surface pits at Oaky Creek North and submitted to Auralia Metallurgy in Perth for ore characterisation, crushing, grinding, and flotation testing. Assay work — including Fire Assay for gold, Mixed Acid Digest/ICP-MS for silver, and XRF BM for all other elements — was conducted at ALS Global Laboratories in Perth, a NATA-accredited facility.

The results speak clearly:

• Head grade of 19.9% Sb and 0.25ppm Au, which sits comfortably within the range of previously reported mineralised rock chip grab samples from the prospect (up to 39.3% Sb and 1.09ppm Au)
• Composite concentrate grading 51.8% Sb at a 29.7% mass pull, achieved with a total flotation time of just 14 minutes
• 85% antimony recovery relative to head grade — an exceptionally high result for a first-pass pilot study
• Arsenic returned below detection at <0.01%, and the final concentrate contained only 197ppm As — a critically low level for a deleterious element that can complicate processing and marketability
• Gold recovery into the concentrate was 32.8% at 0.07ppm, suggesting gold is largely locked in solid solution and not readily recoverable through standard flotation

The reagent suite used — lead nitrate activator, potassium aryl xanthate (PAX) collector, and glycol ether-based H57 frother — is standard for sulfide ores of this type, reinforcing that no exotic or costly processing chemistry is required.

"The concentrate would be an excellent feedstock 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 programme."

— Red Mountain Mining ASX Announcement, 25 May 2026

Metallurgical Results at a Glance

A Clean Ore Profile: Why Mineralogy Matters

Detailed mineralogical characterisation using Tescan Integrated Mineral Analyser (TIMA) and semi-quantitative X-ray diffraction (XRD) confirmed that almost all antimony in the sample occurs as stibnite (Sb₂S₃) — the primary, processable antimony sulfide mineral. This is a particularly important finding, as it means the ore responds predictably to conventional flotation.

Mineral Composition of the Oaky Creek Bulk Sample (Combined)

Key takeaways from the mineralogy include the following:

• Other sulfides and tellurides total just 0.05% — consistent with the below-detection assay results for arsenic, copper, lead, and zinc, all of which can be problematic in antimony concentrates
• Quartz dominates the gangue at 50.5%, making for a relatively straightforward separation environment
• A coarse grind of P80 = 212µm was sufficient to achieve the standout recovery result, which suggests lower energy consumption in a production scenario compared to finer-grind operations
• Oxidised stibnite phases collectively represent only ~5.08%, meaning the ore is predominantly fresh and amenable to sulfide flotation

Understanding Flotation and Why an 85% Recovery Is Exceptional

What Is Flotation?

Flotation is one of the most widely used methods in mineral processing to separate valuable minerals from gangue (waste rock). Crushed ore is mixed with water and chemical reagents in a tank. Air is bubbled through the slurry, and the target mineral — in this case stibnite — attaches to the bubbles and floats to the surface, where it is skimmed off as a concentrate.

The "recovery" figure describes what percentage of the target metal in the original ore ends up in the final concentrate.

Why Does 85% Recovery Matter?

In a commercial mining context, higher recovery means more of the valuable mineral is captured and sold, directly improving project economics. For context, the initial target set for this testwork was a concentrate grading 30–40% Sb at >70% recovery. The actual result — 51.8% Sb at 85% recovery — significantly exceeded both thresholds in a single first-pass study.

This is, furthermore, a strong early indicator that the ore is well-suited to conventional processing and that further optimisation could yield additional improvements.

Glossary of Key Terms

The Oaky Creek System: A 3km Orogenic Target with Five Drill-Ready Zones

The metallurgical result does not exist in isolation — it validates a mineralogical system that has been systematically de-risked through more than a year of surface exploration work. Oaky Creek features quartz-carbonate-stibnite veins and breccias hosted within folded and faulted Carboniferous metasediments, a geological setting analogous to other significant orogenic antimony deposits in the Southern New England Orogen (SNEO).

Surface exploration at Oaky Creek has, consequently, delivered:

• A coherent ~1.5km long, 100–200m wide NNW-trending soil anomaly at Oaky Creek North (>2ppm Sb), extending both north and south of historical workings
• A similarly oriented ~1km long >2ppm Sb soil anomaly at Oaky Creek South
• Multiple rock chip samples returning values above 25% Sb and 0.1g/t Au across five separate mineralised areas
• Approximately 1,300 infill hand auger soil samples completed across the full ~3km strike extent of the prospect, tightening the grid from 100m x 50m spacing to support precise drill target definition
• Five high-priority drill targets defined and ready for testing

The announcement also notes that the system is described as being analogous to Larvotto Resources' (ASX: LRV) Hillgrove Project — a nearby deposit that represents Australia's largest known antimony deposit and ranks as the 8th largest antimony deposit globally. Larvotto Resources carries a market capitalisation of approximately AU$610 million as a reference point for the potential scale of orogenic antimony systems in this region.

Red Mountain's 100%-owned Armidale Antimony-Gold Project holds 391km² of tenure along an 85km strike length on the western side of the Peel Fault — a structure with over 400 known orogenic gold and base metal mineral occurrences along its more than 400km total strike extent. The majority of these occurrences remain underexplored, with fewer than 200 mostly shallow drillholes across its length.

What Comes Next: The Upcoming Drilling Programme

The metallurgical study was explicitly framed as a first-pass exercise aimed at developing a viable processing flowsheet. With the result exceeding commercial thresholds in the first attempt, Red Mountain is now advancing directly to drilling rather than undertaking additional bench-scale optimisation at this stage.

Planned near-term activities include:

1. RC drilling programme — approximately ~2,000m across five priority targets at Oaky Creek, approved by the NSW Regulator. A drill rig is currently being secured.
2. Ground IP survey results — a completed ground IP (induced polarisation) geophysical survey, with results awaited, is expected to assist in refining drill collar locations by delineating hydrothermal zones associated with antimony mineralisation.
3. Pyrometallurgical testing — roasting of the concentrate is identified as the next processing stage, planned with a larger sample volume.
4. Further metallurgical refinement — post-drilling, additional testing along strike will check for grade continuity and metallurgical consistency across the system.
5. Pioneer Tungsten Project due diligence — the company confirmed that due diligence at the Pioneer Tungsten Project in Beaverhead County, Montana (USA) is progressing well and on schedule under the existing option agreement.

Upcoming Milestone Timeline

The Investment Case: Why These Results Matter

The Red Mountain Mining Oaky Creek antimony metallurgy results are significant for several interconnected reasons that go directly to project quality and development de-risking.

1. Concentrate quality far exceeds the commercial standard.
A grade of 51.8% Sb is not marginally above the 30–40% commercial range — it sits materially higher, indicating a clean, high-value product that would be a premium feedstock for pyrometallurgical refining into saleable antimony metal.

2. The ore is amenable to standard, low-cost processing.
A coarse grind (P80 = 212µm) and a 14-minute flotation circuit using conventional reagents produced these results. There is no indication of complex mineralogy, exotic processing requirements, or refractory behaviour that could complicate or inflate processing costs.

3. Arsenic — the industry's most feared deleterious element in antimony — is essentially absent.
The head grade returned <0.01% As, and the final concentrate carried only 197ppm As. Elevated arsenic content is one of the most common obstacles to marketing antimony concentrates and can severely limit smelter offtake options. At Oaky Creek, however, this concern appears to be materially resolved.

4. The system is large, coherent, and systematically characterised.
A 3km orogenic system with five defined drill targets — underpinned by ~1,300 soil samples, multiple high-grade rock chip results, and now exceptional metallurgy — represents a genuinely well-progressed exploration story relative to the company's stage of development.

5. Drilling is the value-defining next step.
The critical unknown is depth continuity. The upcoming ~2,000m RC programme will test whether the high-grade surface mineralisation extends at depth with sufficient volume to support a resource. If it does, the combination of high-grade ore and exceptional metallurgy creates a compelling foundation for a development study.

Why Investors Should Keep a Close Eye on Red Mountain Mining

Red Mountain Mining is advancing a critical minerals portfolio at a time when antimony — classified as a critical mineral by multiple Western nations — faces meaningful supply constraints, with global production heavily concentrated in China. The company holds 100% of a large, well-located tenement in Australia's premier antimony province, adjacent to a globally significant antimony deposit, and has now demonstrated that its highest-priority prospect produces concentrates of exceptional commercial quality.

The upcoming drilling programme is the most material near-term catalyst for the company. A positive drill result confirming depth extensions to the high-grade mineralisation would mark a step-change in the project's development trajectory and would, for the first time, provide the data required to estimate a JORC-compliant mineral resource.

The combination of exceptional surface grades (up to 39.3% Sb in rock chips), a clean ore profile (arsenic below detection), world-class Red Mountain Mining Oaky Creek antimony metallurgy results (51.8% Sb concentrate at 85% recovery), a well-characterised 3km system, and an imminent drill programme targeting five defined zones makes this one of the more compelling near-term catalysts in the Australian critical minerals exploration space.

Key Takeaway:

Red Mountain Mining has established Oaky Creek as a genuinely high-quality antimony prospect, delivering a concentrate that exceeds commercial grade thresholds at exceptional recovery rates — all from a first-pass pilot study. With five drill targets approved for testing and a rig being secured, the company is on the cusp of the most consequential phase of its exploration programme to date. Investors tracking the critical minerals space should have RMX firmly on their radar.

All figures and data sourced from the Red Mountain Mining ASX announcement dated 25 May 2026. This article is for informational purposes only.

Ready to Learn More About Red Mountain Mining's Oaky Creek Project?

With exceptional metallurgical results already in hand and an RC drilling programme imminent across five priority targets, Red Mountain Mining (ASX: RMX) is entering one of the most significant phases in its exploration history. To stay across the latest developments at the Armidale Antimony-Gold Project and learn more about the investment case for RMX, head to the Red Mountain Mining InvestorHub.