Further analysis of high silica assays from the Mount Ridley REE project north of Esperance has increased already high REE mineralisation grades, some by up to 202%.

A recently completed 81 AC drill campaign for 4,083m predominantly at Mount Ridley Mines’ (ASX:MRD)  advanced Mia prospect defined REE mineralisation ranging between 3m and 41m, with an average thickness of ~12m.

Multiple, parallel, high-grade trends of clay-hosted REE mineralisation with grades  over 1000 parts per million (ppm) total rare earth oxides (TREO) were outlined within a 3km wide zone, over a length exceeding 16km, that remains open to the northeast and southwest.

Beneficiation breakthrough

Screen beneficiation testing on 19 samples has returned huge increases in REE grades, MRD says.

Beneficiation is a process which removes barren minerals from mineralisation to achieve an improvement in grade.

Think of it like putting flour through a sieve, and the micron level is the amount of space between the mesh squares – only the finer particles will get through.

Of the 19 samples – taken from 15 targeted drill holes – beneficiation tests are showing that >80% of the TREO is contained within 50% of the original sample mass, and the barren proportion can be rejected when simply screened at 75 microns.

To test that “75” number, MRD said a range of screens with apertures between 500 micron (μm) and 25μm were used, with results showing that optimum beneficiation – being the relationship between mass rejected and REE recovered – was achieved by screening at 75μm.

The screened 75μm samples provided whopping upgrades to the samples, such as:

  • a 172% upgrade (2,771 ppm to 4,759 ppm TREO) from Mia MRAC1180 from 9m to 17m,
  • 140% upgrade (1,477 ppm to 2,062 ppm TREO) from Mia MRAC1184 from 30m to 59m,
  • 156% upgrade (6,304 ppm to 9,848 ppm TREO) from Mia MRAC1188 from 69m to 74m,
  • 151% upgrade (1,480 ppm to 2,229 ppm TREO) from Jody MRAC1162 from 18m to 53m,
  • 162% upgrade (2,470 ppm to 4,003 ppm TREO) from Vincent MRDD0029 from 30m to 34m,
  • 130% upgrade (1,871 ppm to 2,440 ppm TREO) from Fabienne MRAC1259 from 30m to 42m,
  • and a 202% upgrade (498 ppm to 1,007 ppm TREO) from Vincent MRAC1109 39m to 56m. 
Mount Ridley
Highly enriched REE intersections at the Mia prospect at Mount Ridley. Pic supplied (MRD).

What’s an REE you say?

REEs refer to the 14 “common” rare earth elements.

These elements are cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), samarium (Sm), terbium (Tb), thulium (Tm), ytterbium (Yb).

Yttrium (Y) is usually included with REE because you’ll likely find it there along with the others.

TREO means the sum of the 14 REE+Y, each converted to its respective stoichiometric element oxide.

Moving ahead

“Beneficiation results have delivered an important breakthrough, identifying the ability to substantially increase the grade of REE mineralisation through an inexpensive, simple, and broadly adopted mineral processing technique,” MRD chairman Peter Christie said.

“The company believes that targeted drilling throughout the central zone of the Mia prospect can generate intersections at grades high enough to ultimately beneficiate above 2,000ppm TREO, which will have a very positive impact on project economics.”

Fifteen samples from the Mia, Jody, Winston and Vincent prospects, having been screened to -25 microns, are undergoing leach testing by ANSTO and Independent Metallurgical Operations (IMO) laboratories.

On the back of these impressive beneficiation results, the company is now targeting high silica-kaolin clays for additional metallurgical testing with work approvals already having been granted.




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.