Lepidolite vs Spodumene
Lepidolite and Spodumene are genuine alternatives to one another — a choice somebody actually makes — and differ on 4 measured properties, cleavage most clearly.
Lepidolite vs Spodumene
Lepidolite
K(Li,Al)3(Si,Al)4O10(F,OH)2
A lilac lithium mica — the second lithium ore, and the main mineral source of rubidium and caesium alongside it.
Spodumene
LiAlSi2O6
A lithium aluminium silicate from granite pegmatites — the hard-rock source of lithium, and the one that does not depend on a salt flat.
| Property | Lepidolite | Spodumene |
|---|---|---|
| Cleavage Categorical values can be listed side by side but not ordered or subtracted. | perfect in one direction, splitting into flexible sheets | perfect in two directions |
| Crystal system Categorical values can be listed side by side but not ordered or subtracted. | monoclinic | monoclinic |
| Density | 2.8–2.9 g/cm³ | 3.1–3.2 g/cm³ higher |
| Lustre Categorical values can be listed side by side but not ordered or subtracted. | pearly | vitreous |
| Mohs hardness Mohs hardness is an ordinal scale: values can be ranked, but differences and ratios between them are not meaningful. | 2.5–3 | 6.5–7 higher |
| Streak Categorical values can be listed side by side but not ordered or subtracted. | white | white |
Choosing between them
Lepidolite is recorded as a substitute for Spodumene — less supply-constrained.
What it gives up: Lower lithium content and fluorine that complicates the roast.
Partial substitute, on the evidence cited above.