Are Ionic Adsorption Clay Deposits a Game-Changer for the Supply of Rare Earths

Are Ionic Adsorption Clay Deposits a Game-Changer for the Supply of Rare Earths

Rare earths are a key building block in critical components found in modern technologies such as electric vehicles, wind turbines, and smartphones.

Over the last two years, there has been an abundance of discoveries of rare earths mineralization called Ionic Adsorption Clay (IAC), characterized by the extensive low-grade deposits in Southern China. Australia leads the way due to its long-lived and continent-wide deeply oxidized weathering environment considered necessary for these deposits to form. Barely a week goes by without a new discovery. But are these deposits genuinely IAC and does it matter?

While the abundance of these deposits has sparked investor interest, questions remain about their true nature and the economic viability of development.

The types of rare earths deposits

We need to set the scene for rare earths (REE) deposits to answer that question. REE deposits are well documented and are dominated by:

  • Alkaline igneous rocks such as carbonatites, granites, and felsic volcanics;
  • Hydrothermal altered calc-silicate sequences; and,
  • Secondary regolith clay-hosted deposits. 

Reworked alluvial accumulations rich in monazite are clearly a separate type but becoming increasingly important as a competing source of REEs.

Regolith clay hosted deposits and the formation of IAC deposits

Regolith deposits develop by the weathering of the underlying host rock to form a variety of secondary clays and other oxidized products. Important source rocks typically have a relatively high background in rare earths and rare earth bearing minerals in these rocks will include monazite, xenotime, bastnaesite, allanite, titanite, and apatite.

Minerals like bastnaesite, allanite, and titanite are most susceptible to the acidic ground waters that develop in the upper levels of humus-rich soils in temperate or tropical climates, with moderate to high temperatures and rainfall. The REEs from the decomposed minerals migrate downwards as REE-ions in solution which can adsorb onto clay minerals such as kaolinite and become IAC deposits. 

Alternatively, the percolating solutions can combine with phosphate or carbonate to form secondary minerals (often in a colloidal phase) in a neutralization step. The more resistive minerals such as monazite and xenotime remain unaltered and can accumulate physically with partial removal of the surrounding oxidized rock by the weathering process.

The “does it matter” question

So we have the three types of rare earth accumulations in a regolith profile which gets us to the “does it matter” question.

The geometallurgy, capital expenditures (CapEx), and operating expenditures (OpEx) of a mining and processing facility, and the marketability of any products produced drive the economic development of any rare earths deposit. 

In regolith deposits, the Chinese found that weakly acidic ammonium sulphate or sodium chloride solution readily reclaims the rare earths from the ionic bonded clays allowing the resulting crude solution to be chemically treated to eliminate contaminants for further solvent extraction separation and refining. This processing can be in-situ leaching; heap leaching; or in-tank leaching with increasing cost and all with significant environmental impact. 

Generally, Chinese costs for REE reclamation from IAC deposits are low and despite the low recoveries peaking at around 30% to 40% in final products, these projects appear to be economic.

Economic challenges of other regolith deposits

The other regolith deposits require more sophisticated processing with higher costs from increased upfront chemical consumption (sulphuric acid) after mining from open-cut operations and subsequent processing, including removal of significant contaminants from the acid leaching. There have not been many colloidal-type deposits identified to date, and it appears many of the new group of announced deposits could be clay-hosted, residual monazite-xenotime accumulations and not true IAC. Solubilizing monazite and xenotime is a known commercial process and the costs are well-defined but are significantly greater than for IAC extraction. The processes to recover REs from resistate minerals in the near horizontal deposits at depth will require environmentally sustainable mining, potentially covering large areas.

If this is the case then it will be very interesting to see how many of these low-grade, sub 2,000 parts per million (ppm) or 0.2% of total rare earth oxides, will be economical to produce or do they have a touch of hype at present. 

Final thoughts

The economic viability of IAC deposits remains uncertain, with questions about their true nature and the costs of mining and processing. While the Chinese appear to have developed a low-cost method of reclaiming rare earths from IAC deposits, other regolith deposits require more sophisticated processing with higher costs and the potential for significant environmental impacts.

So, yes investors would be wise to understand the deposit type and geometallurgy before investing.

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5 responses

  1. Alastair Avatar

    These deposits have one benefit and that is the low levels of cerium which raises the content of the other elements. With oversupply of cerium and prices under $1/kg this eliminates the need to find a home for large volumes of cerium. The other benefit is that a concentrate of 92% TREI can be made with simple chemistry which reduces freight costs.

  2. Jack Lifton Avatar
    Jack Lifton

    The tiny amount of higher atomic numbered rare earths to be economically recovered outside of southeast Asia from ionic adsorption clays will not change the rare earth permanent magnet equation. Unless new techniques of manufacturing magnets are devised then only those that have access to all of the rare earth elements necessary to produce industrial permanent magnets capable of withstanding large numbers of cycles of heating and cooling will dominate the market. There will be winners and losers among those for whose products temperature resistant permanent magnets are necessary. This fact is only now slowly sinking into the heads of those, non Chinese, responsible for sourcing permanent magnet enabled components for machinery. China is today the only nation self sufficient in the total supply chain necessary to supply its manufacturing base with the complete range of rare earth permanent magnets. Ultimately other nations will only be able to manufacture rare earth permanent magnet dependent products to the limit of what they can produce domestically or procure outside of China. Right now, if China stopped exporting rare earth permanent magnet enabled components the non-Chinese industrial manufacturing world would go into a deep recession.

  3. Bruce Barker Avatar
    Bruce Barker

    Very good article by Ian Chalmers in helping to understand IAC rare earth deposits , and Jack’s comments on China are spot on . Thus ..other viable long term exChina deposits have to be found and brought into production . One such exceptionally good discovery is in Brazil , via an ASX Australian listed company Meteoric Resources ( MEI ) , where the TREO grades are world class , from surface ..and the Resource being proved up is size and scale ! Good one to watch the current news flow unfolding , with Presentations expected soon .
    Always enjoy the articles on this site , to broaden knowledge in such an important area

  4. Bruce Avatar

    Regarding ASX:MEI Meteoric Resources as referred to above with a high grade Ionic Clay Rare earth deposit at Caldeira , Brazil . As it so happens , an Investor Presentation was lodged with the ASX TODAY . Link attached
    Well worth looking at the Maiden Inferred Resource based on past drilling , the exceptionally high grades from surface , and the programme going foward .

  5. Rare Earths Investor Avatar
    Rare Earths Investor

    As a RE retail investor, I am always looking for articles to create more investor related questions. For me, the article and comments raise the following questions. For example, is anyone concerned about the recently arrived Lula and his environmental drive and impact on potential RE mining projects in Brazil? Note, he’s a close follower of Biden who himself seems unable be to even talk positively on new within borders critical metals mining, never mind permits.

    So, all this RE feedstock availability is fine, but regardless of its source, what about the ROW processing availability (and the magnet-making, oh boy)? The stuff stays in the ground if there is no processing for it (unless it goes we know where).

    As far as I am aware, NEO and Lynas are the only ROW masters here and that’s LRE (not HRE). Solvay and MP have long past experience (SRC?). Note the very slow present approach to processor buildout in the US (Lynas, MP and REEMF; then, Ucore and Energy Fuels?). Not to mention the very recent extraction dead stop by Vital Metals.

    Fears of ROW recession, potential oversupply, crashing prices, rampant inflation, lack of ROW processing and magnet-making destinations, OEM indecision, etc, etc.

    Yes, I agree, I think the nature of a RE feedstock source is important but represents only one variable in this complex process. As to a ‘game changer’, I have my doubts and retail investors should think much more macro in terms of how their micro investment considerations might have a slim chance of actual emergence.

    Thanks very much for writing the article, anything that creates left-field questions can only help all of us small-time RE investors.


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