Rare earths do not come from one ore mineral. Bastnäsite, monazite, loparite and ion-adsorption clays can require fundamentally different preparation routes.
- Major sources
- Bastnäsite, monazite, loparite and ion-adsorption clays
- Critical distinction
- Hard-rock versus clay-type sources
- Preparation objective
- Condition valuable phases for suitable downstream separation
Why can rare-earth ore not be described by one flowsheet?
Rare earths occur in different minerals and deposit types. A hard-rock bastnäsite or monazite ore does not require the same comminution approach as an ion-adsorption clay.
Mineralogy, particle size and the host phase of the valuable elements define the scope of mechanical preparation.
How should hard-rock preparation be approached?
For hard-rock feed, crushing and controlled grinding aim to liberate rare-earth-bearing minerals from gangue. A fixed P80 should not be specified before the liberation size is tested.
Excessive fines can complicate some downstream separations, so staged liberation and classification may be important.
Why are clay-type sources different?
In ion-adsorption clays, valuable elements may not be locked inside a coarse crystalline ore mineral. Intensive grinding therefore does not play the same role as in hard-rock ore.
Chemical extraction or leaching is a separate stage from mechanical ore preparation; this section explains the role and limits of mechanical preparation for each source type.
Core ore-characterization questions
- Which mineral or phase carries the rare earths?
- Is the source hard rock, sand or clay?
- What is the liberation size?
- Is value lost in the fine fraction?
- What feed properties are required by the downstream separation step?