Bastnäsite vs Monazite
Bastnäsite and Monazite are genuine alternatives to one another — a choice somebody actually makes — and differ on 4 measured properties, crystal system most clearly.
Bastnäsite vs Monazite
Bastnäsite
(Ce,La)CO3F
A rare earth fluorocarbonate — the principal ore of the light rare earths, and the mineral behind most magnets in the world.
Monazite
(Ce,La,Nd,Th)PO4
A rare earth phosphate that carries thorium with it — the other major rare earth ore, and the reason their processing leaves radioactive residues.
| Property | Bastnäsite | Monazite |
|---|---|---|
| Crystal system Categorical values can be listed side by side but not ordered or subtracted. | hexagonal | monoclinic |
| Density | 4.9–5.2 g/cm³ higher | 4.6–5.4 g/cm³ |
| Lustre Categorical values can be listed side by side but not ordered or subtracted. | vitreous to greasy | resinous to waxy |
| Mohs hardness Mohs hardness is an ordinal scale: values can be ranked, but differences and ratios between them are not meaningful. | 4–5 | 5–5.5 higher |
| Streak Categorical values can be listed side by side but not ordered or subtracted. | white | white |
Choosing between them
Bastnäsite is recorded as a substitute for Monazite — lower environmental impact.
What it gives up: Carries fewer heavy rare earths, so a bastnäsite operation does not supply dysprosium.
Direct substitute, on the evidence cited above.