Spodumene is super expensive; one dunk in a dipping glaze can now cost dollars. But lithium carbonate is even more so. However, both are used as a source of Li2O. The latter is 6+ times more concentrated. And spodumene is more troublesome in glazes (issues with settling, dusting, slurry properties, consistency). And it can be hard to get. So using the pure lithium material might be a better choice for you.
This side-by-side calculation seems to indicate that 15 Lithium Carbonate, 55 Kaolin and 30 Silica can substitute for 100 parts by weight of Laguna Spodumene Substitute. However, that is not quite correct. Note that my substitute recipe calculates to an LOI of 16.3. If I assume the Laguna material has no LOI (for convenience, it actually has 0.2%), that means each of the amounts need to be divided by (100-16.3)/100=0.84. Thus, to substitute for 100 parts of spodumene, you need ~120 of this mix (18 lithium carbonate, 66 kaolin and 36 silica).

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Lithium carbonate is now ultra-expensive. Yet the reactive glaze on the left needs it. Spodumene has a high enough Li2O concentration to be a possible source here. It also has a complex chemistry, but the other oxides it contains are those common to glazes anyway. Using my account at insight-live.com, I did recipe rescue calculations and got a pretty good match in the formulas (lower section in the green boxes). Then I made 10-gram balls and did a GLFL test at 2200F (notice the long crystals in the glass pools below the runways).
Not surprisingly, this recipe is very runny; that's why the tiny yellow crystals grow during cooling. The new version fires very similarly, perhaps better. Our calculated cost to mix this recipe in 2022 was $17.84/kg vs. $10.40/kg. In 2026 it is triple that! But there is a practical cost: Poor slurry properties. The spodumene sources so much Al2O3 that 70% Alberta Slip had to be dropped to accommodate it! How does one use this type of glaze without ruining kiln shelves? Using a catcher glaze is one answer.
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