• Leach testing has achieved up to 85% recovery of magnet REEs
  • Results achieved a ‘reasonable level of acid consumption’
  • Drilling to resume at Mia prospect in September


Leach testing of beneficiated samples taken across Mount Ridley’s namesake project north of Esperance, WA, has delivered high rare earths extraction rates including up to 85% recovery of valuable magnet REEs.

The emerging Esperance REE province that has been shown to have high percentages of neodymium and praseodymium (NdPr), dysprosium and terbium.

These high value REEs are used in the production of permanent magnets for electric vehicles and wind turbines, two massive growth industries.

Extraction rates of up to 72% of the total rare earth oxides (TREO) content were achieved at the key Mia and Vincent prospects using a simple hydrochloric acid leach, including up to 85% of these magnet rare earths.

It follows Mount Ridley Mines’ (ASX:MRD) successful use of simple screen beneficiation at 75 microns – essentially sieving out the barren proportion of the clay-hosted mineralisation — which returned an average grade upgrade of 164% from Mia and 154% from Vincent, to collect over 80% of the TREO within 50% of the original sample mass.

This effectively increased the weighted average drill-intersection grade at Mia from more than 1,500 parts per million TREO to over 2,400ppm TREO, which has the potential to significantly improve economics by reducing the amount of material that needs to be processed.

“Recent results have provided valuable metallurgical insights as the company progresses towards a flow sheet for the Mia prospect and the larger Mount Ridley REE project,” chairman Peter Christie said.

He added that the excellent acid leach test results from beneficiated test samples demonstrated the potential efficacy of hydrochloric leaching to recover REEs at a reasonable level of acid consumption.

“We are looking forward to resuming drilling and metallurgy at the Mia prospect in September ahead of the company’s maiden Mineral Resource estimate later in the year,” Christie noted.


Big potential footprint

The 3,400km2 Mount Ridley project about 50km northeast of Port of Esperance presents a large, highly prospective area for the company to explore in.

Previous work had identified the presence of REE’s within a zone of about 30km by 11km while during the June 2023 quarter, the company drilled 81 resource definition aircore holes totalling 4,083m at the central Mia prospect. This represents about 30% of the current drill program.

Drilling within the target 16km long by 3km wide clay corridor has returned thick, high-grade intersections including a project high of 36m grading 4,398 parts per million TREO – with 23% magnet REO.


A bustling clay REE province

There are several other juniors that have also staked out sizeable landholdings in the region and enjoyed significant successes in their hunt for MREO-rich clay-hosted REE mineralisation.

Companies such as OD6 Metals (ASX:OD6), West Cobar Metals (ASX:WC1) and Heavy Rare Earths (ASX:HRE) have all reported strong REE drill hits with the latter two having defined maiden resources.

There is good reason for all this activity. Clay-hosted mineralisation has the potential to be cheaper to both mine and process compared to hard rock deposits, especially if they can be proven to be of the ionic adsorption type that’s typically found only in China.

The high MREO component is also hugely positive as these elements are critical in the manufacture of permanent magnets that are used in electric vehicle motors or wind turbines.


Maiden resource later this year

Assays from infill aircore holes drilled at the Mia prospect earlier this year are currently being received and compiled, for an expected release date in early to mid-September.

The company also expects to resume drilling the same month with the aim of defining a maiden resource later this year.

This infill drilling of 180 holes totalling about 9,000m will seek to bring the drill density down generally to a 400m by 400m grid.

Mount Ridley has also received Programmes of Work approvals from the DMIRS5 (subject to completing heritage and flora surveys) to drill throughout the 16km long Mia-Marvin Trend while approvals are already in place to drill in and around the Vincent prospect to follow up the excellent metallurgical results reported herein.




This article was developed in collaboration with Mount Ridley Mines, a Stockhead advertiser at the time of publishing.


This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.