Introduction
These are not “minerals” in the traditional hard-rock sense. Ionic Adsorption Clays are weathered granite deposits found primarily in Southern China and Myanmar. Over millions of years, rare earth elements were dissolved from the bedrock and “stuck” (adsorbed) onto the surface of microscopic clay particles.
Composition & Chemistry
The beauty of these deposits is that the rare earths are not locked inside a tough crystal lattice. They are weakly bonded to the clay.
Processing: The “Tea Bag” Method
Mining does not require crushing or grinding rock. Instead, miners use “In-Situ Leaching” or heap leaching. They pour an ammonium sulfate solution over the clay, which swaps places with the rare earths, washing them out into a collection pool. It is chemically simple and cheap.
The Double-Edged Sword
- Pro: They are the world’s dominant source of Heavy Rare Earths (Dysprosium/Terbium) without the radioactivity of Xenotime.
- Con: Historical mining methods have caused massive environmental damage, including groundwater contamination and landslides, leading China to crack down heavily on illegal clay mining.