As they say in the classics, "tonnes ain't tonnes" :) Molecular...

As they say in the classics, "tonnes ain't tonnes"

Molecular weights:
Lithium: 7; Carbon: 12; Oxygen: 16

I believe "6% spodumene concentrate" refers to concentrate containing the equivalent of 6% of lithium oxide (Li2O) which has a molecular weight of about 30, compared to lithium carbonate (Li2CO3) which has a molecular weight of around 74.

So a tonne of lithium carbonate contains around 14/74 a tonne of lithium (19%);
a tonne of lithium oxide contains around 14/30 a tonne of lithium (47%)

That would explain why the hardrock concentrate prices seem so high compared to carbonate.