Locksley Resources antimony grades run hot in US desert project
- Doug Bright
- 7 hours ago
- 4 min read
Locksley Resources Limited (ASX: LKY) has announced standout results from a targeted batch sampling program at its Desert Antimony Mine prospect within its Mojave project in California’s San Bernardino County.
The batch sampling program builds on prior successes, including a 325-kilogram bulk sample with a head grade of 7.6 to 7.8 per cent antimony and initial flotation testwork late last year that produced a premium 68.1 per cent antimony concentrate.
The latest sampling program collected 287kg of antimony-mineralised material from historical underground workings, focusing on specific vein zones to support metallurgical optimisation and pilot plant design.
Eleven samples across three batches returned impressive antimony grades, up to a peak grade of 26.1 per cent antimony from one sample of high-grade material in Batch 2.
With these results, added to the imminent arrival of the drill rig at Mojave, we are entering a very exciting time for Locksley.
Locksley Resources Managing Director and CEO Kerrie Matthews
Batch 1 comprised two samples, totalling 55.56kg of stibnite (antimony sulphide)-rich material, which delivered a weighted-average grade of 25.7 per cent antimony.
The second batch comprised 130kg of high-grade material across five samples, with an average antimony grade of 21.3 per cent.
A third batch of four samples, totalling 99kg, consisted of lower-grade material included to ensure the program was representative overall and returned an average grade of 11.4 per cent antimony.
The overall weighted average grade across all three batches was 18.7 per cent antimony, marking a substantial upgrade from the previous bulk sample.
Unlike many global antimony resources, where the silvery-black metal is often a by-product, Locksley’s project appears to host clean, primary, high-grade potential, ideal for premium concentrates that can be delivered through simpler flowsheets, lower reagent use, and higher recoveries.
For Locksley to consistently return double-digit percentages at over 25% underscores the potential of the Desert Antimony Mine. We aren’t just looking at by-product antimony, we are looking at a rich, primary source of a metal that the U.S. Department of Defence and the energy sector desperately need.
Locksley Resources Managing Director and CEO Kerrie Matthews
This latest round of sampling focused on clean, stibnite-rich veins to confirm grade consistency and assess how the rocks behave during processing. Early signs are encouraging. The high-grade material means less rock needs to be processed, power use can be lower and metal can be recovered faster — all of which point to a smaller, more efficient processing plant.
The data will ultimately feed into a proposed phase one pilot processing program.
Locklsey says the results have also reinforced its “mine-to-market” strategy for antimony trioxide and trisulfide, both of which are key for US defence, semiconductors and flame retardants.
Adding to the project’s credentials, the sampling data appears to complement the company’s previous LiDAR mapping of about 236 metres of underground workings and its recent mapping of structural extensions. Those surveys delivered a four-fold increase in target strike length, for a target corridor up to 1.2km long.
The results also go some way to validating the company’s recent maiden exploration target, which is estimated at between 19,400 and 67,000 tonnes of contained antimony.
The Desert Antimony Mine is a historical antimony producer in the arid Mojave Desert setting, with old underground adits, stopes, and shafts. Adits are horizontal drives into a mine from the slope of a hill. Stopes are ore-mining excavations, while shafts are vertical or inclined accessways between levels.
It is one of only a handful of legacy antimony sites in California and hasn’t seen real action for decades. Now, Locksley is looking to breathe new life into the old workings as it pushes towards near-term domestic production, lining up neatly with the United States’ growing focus on securing its own critical minerals supply.
Next up, the 287-kilogram sample will go through advanced flotation and crushing tests to fine-tune the processing approach, alongside engineering work for the planned pilot plant. At the same time, Locksley will push ahead with mine permitting and extraction planning, working closely with US-based consultants.
Adding further gravitas to Locksley’s antimony story is its proximity to MP Materials’ Mountain Pass mine, lying only three kilometres north-northwest of the mammoth operation. Mountain Pass is the only operating rare earths mine in the US and produces over 15 per cent of global rare-earths oxide equivalent.
In December last year, Locksley announced the outcome of a high-resolution helicopter-borne magnetic and radiometric survey, which identified a pronounced thorium anomaly in its North Block claims.
Thorium is a key indicator for potential rare earth elements mineralisation. Intriguingly, the anomaly lies within the same geological district as the Mountain Pass mine, which is also backed up by a strong thorium signature.
As global antimony supply tightens and US domestic needs escalate, Locksley’s high-grade batch results from its Desert Antimony Mine look set to accelerate the company’s momentum towards potential production.
With premium concentrate pathways proven and pilot work advancing, Locksley’s Mojave project stands out as a compelling US critical minerals play that could also expand to include rare earths.
The company’s following updates on its antimony flotation optimisation and extraction milestones will be keenly awaited.
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