Cracking & Leaching

Rare earth cracking and leaching is the chemical step that breaks down a mineral concentrate, dissolves its rare earths and purifies them into a mixed rare earth product, usually a carbonate or oxalate, ready for separation. The International Energy Agency calls it the transition from physical to chemical processing, one that depends heavily on reagents, water and the handling of radioactive by-products (IEA, May 2026).

Where rare earth cracking and leaching sits in the supply chain

The IEA lists the chain as extraction, beneficiation, chemical upgrading, separation into oxides, metal refining, alloying and magnet manufacturing. Beneficiation, part of mining, turns crushed ore into a mineral concentrate. Chemical upgrading leaches and purifies that concentrate into mixed rare earth compounds, which then go to separation (IEA).

How rare earth cracking works: acid baking and caustic digestion

Cracking converts a concentrate into soluble rare earth salts, such as sulfates, chlorides or carbonates. A 2022 review in MRS Bulletin names two main routes: roasting with sulfuric acid, used at Baotou in China and Kuantan in Malaysia, and hydrochloric acid, used for bastnäsite in Sichuan (Zapp et al., 2022).

In acid baking, sulfuric acid turns the fluorocarbonate in bastnäsite and the phosphate in monazite into rare earth sulfates. The roast emits sulfur dioxide, plus hydrogen fluoride from bastnäsite, though exhaust-gas scrubbing can cut both sharply (Zapp et al.). A 2025 review focused on Chinese practice calls roasting with concentrated sulfuric acid at 150 to 300°C the most widespread industrial method. It puts the waste residue at about 1.2 to 1.4 metric tons per metric ton of concentrate, measured as rare earth oxide (Zhou et al., ACS Omega, 2025).

Monazite can also be cracked with caustic soda. India's Bureau of Mines describes ground monazite digested with caustic soda lye to make trisodium phosphate and a mixed rare earth hydroxide slurry (Indian Minerals Yearbook 2022). Alkaline routes avoid the acid gases, the 2025 review says, but discharge large volumes of wastewater carrying fluorine and phosphorus and need higher-grade concentrate (Zhou et al.).

Leaching to a mixed rare earth carbonate or chloride

In hard-rock operations, the IEA says, cracking, leaching and impurity removal come before the rare earths are precipitated as mixed carbonates or oxalates. Mixed chlorides can also be made, but most commercial flowsheets choose carbonates or oxalates, which are more stable to handle and ship over long distances (IEA).

Ion-adsorption clays skip cracking. The IEA says they can be leached with salt-based reagents instead of acids, citing Serra Verde in Brazil, whose operation USA Rare Earth calls the Pela Ema mine (USA Rare Earth, September 2026).

Thorium, uranium and the waste streams

Rare earth ores often carry thorium and uranium. The IEA says processing concentrates them into tailings and residues, and that monazite-rich deposits in particular leave tailings that need long-term containment (IEA). The 2022 review found that leaching sludge often significantly exceeds the 1 becquerel per gram limit for thorium-232 that classifies material as radioactive waste (Zapp et al.).

At Lynas Malaysia, the residues are a magnesium-rich gypsum called NUF, which Lynas says is non-radioactive, and an iron phosphate called WLP that contains very low level radioactive material (Lynas, October 2025). Under its license renewed in March 2026, the plant must adopt an alternative cracking process so that it no longer produces WLP above 1 Bq/g after March 2, 2031 (Lynas 2026 Annual Report).

Some monazite processors recover the uranium and thorium. In India, uranium from monazite is recovered as nuclear-grade ammonium diuranate and thorium is separated as an oxalate (Indian Minerals Yearbook 2022).

Who cracks and leaches rare earth concentrate

• Lynas Rare Earths, Malaysia and Australia. Lynas cracks and leaches Mt Weld concentrate at its Gebeng plant in Malaysia and its Kalgoorlie facility in Western Australia, where it completed process changes in fiscal 2026, including a continuous precipitation process that Lynas says will improve carbonate quality (Lynas, August 2026).
• IREL, Odisha, India. India's Bureau of Mines reported in its 2022 yearbook that IREL's Rare Earth Extraction Plant at OSCOM produces mixed rare earth chloride, which goes to IREL's Aluva plant in Kerala for separation (Indian Minerals Yearbook 2022).
• SARECO, Stepnogorsk, Kazakhstan. Lindian Resources said in its annual report, dated September 25, 2026, that it had completed the acquisition of the SARECO plant, securing 100% ownership (Lindian, September 2026). In August 2026, Lindian said the plant retains its core cracking, leaching and precipitation circuits and that it was targeting first processing there in the fourth quarter of 2026 from Kangankunde monazite concentrate, while also evaluating alternative feedstock in Kazakhstan (Lindian, August 2026).
• Tronox, Rockingham, Western Australia. In September 2026, Tronox and JX Advanced Metals agreed to fund a definitive feasibility study for Tronox's proposed cracking and leaching plant (Tronox). REEx noted that it would crack monazite and that no financing commitment had been announced (REEx, September 2026).
• Hastings Technology Metals, Kabin Buri, Thailand. REEx reported in August 2026 that Hastings, which has proposed a 49% stake in the Kabin Buri plant, targets mixed rare earth chloride production there in the first quarter of 2027, subject to transaction documents, construction and approvals (REEx).
• Torngat Metals, Sept-Îles, Quebec. In October 2025, Quebec's environment ministry listed sulfation and leaching as the main processes planned for Torngat's Sept-Îles plant (MELCCFP).

Why cracking and leaching costs more outside China

The IEA says crack-leach operating costs are higher outside China, largely because of stricter environmental controls, costlier chemical inputs, energy prices and the management of radioactive by-products. It adds that countries with processing ambitions may lack dedicated disposal sites for radioactive waste (IEA).

Frequently asked questions