Mount Ridley is pushing ahead with exploration at its namesake rare earths project after testing confirmed the REE mineralisation is readily soluble.

The re-assay of 489 composite samples taken from 215 drill holes using a weak aqua regia acid solution found that a grade of about 800 parts per million total rare earth oxides was taken into solution under the conditions trialled.

This solution recovered about 80% of the light REO, 76% of the heavy REO and 80% of the critical REO.

Importantly for Mount Ridley Mines (ASX:MRD), the result supports its belief that its project near Esperance, Western Australia, has the potential to host ionic adsorption clay-hosted REE mineralisation in Eocene-aged sediments of the Salmon Gums Plains.

IAC-style mineralisation is rarely found outside of China and considered to be some of the cheapest and most readily accessible sources of heavy rare earths.

Additionally, the drill holes that returned elevated REE extend over an area 25km long and 3km wide, an indicator that there’s plenty of mineralisation to uncover.

“This analytical program was designed to give an early indication of whether the REE mineralisation was in a readily-soluble state and, while these results are indicative only, they exceeded our expectations and therefore encourages the company to fully commit to advancing the Mount Ridley REE Project through drilling and more advanced metallurgical studies,” chairman Peter Christie said.

Metallurgy and drilling

Mount Ridley noted that the results of the AR digestion tests show that a high proportion of the REE present at the project is extractable using a weak acid solution.

Further test work using new drill samples will be designed to determine if the REE can be extracted by salt solutions under weakly acidic conditions.

This is characteristic of classical IAC-style deposits, which are processed by leaching with a weakly acidic salt solution.

Planning is underway for an extensive aircore drill program that will include:

  • Re-drilling some of the holes that terminated in REE mineralisation;
  • Extending drilling traverses where mineralisation remains open;
  • Reconnaissance drilling to test other regional targets; and
  • Core drilling to provide intact core for regolith studies, geotechnical and metallurgical testing, and to test the quality of some of the significantly mineralised, aircore holes drilled in previous campaigns.




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.