Cracking the Crystal
Rare earth minerals are incredibly stable. To dissolve them, you need aggressive chemistry.
- Acid Roast: Concentrated sulfuric acid is mixed with the mineral concentrate and baked at high temperatures (200°C–600°C). This turns the rare earths into water-soluble sulfates.
- Caustic Crack: For Monazite, a hot sodium hydroxide (lye) solution is often used to break the phosphate bond.
Leaching
The roasted material is washed with water. The rare earths dissolve into the liquid (pregnant leach solution), while impurities like iron and silica remain solid and are filtered out. This is also the stage where radioactive Thorium is typically removed and precipitated for safe storage.