A tonne of lithium carbonate is not a tonne of lithium
Product mass, contained lithium, and lithium-carbonate equivalent answer different questions. Converting between them requires a named compound and a declared basis.
The basis comes before the number.
A plant rated for 10,000 tonnes of lithium carbonate product does not contain 10,000 tonnes of lithium. A mine-production table measured as lithium content is not reporting tonnes of concentrate. Lithium-carbonate equivalent, usually shortened to LCE, is a conversion unit rather than another physical product stream.
USGS states the production basis directly
“Data in metric tons, lithium content, unless otherwise specified.”
That sentence appears above the lithium tables in the U.S. Geological Survey Mineral Commodity Summaries 2026, page 118. The 2025 world mine-production figure is therefore lithium contained in mined output, not the gross mass of ore, concentrate, brine, carbonate, or hydroxide.
The conversion is chemical, not editorial
The Factbook's lithium-conversions-v1 registry uses the CIAAW 2024 abridged atomic weights. Pure lithium carbonate has a formula mass of 73.888. Its two lithium atoms contribute 13.88. One tonne of pure lithium carbonate therefore contains 0.187852 tonnes of lithium.
Turn the ratio around and one tonne of contained lithium equals 5.323343 tonnes LCE. Pure lithium hydroxide monohydrate contains 0.165388 tonnes of lithium per tonne of product, or 0.880416 tonnes LCE.
10,000 t/y carbonate product mass = 10,000 t/y LCE under the pure-compound convention = 1,878.52 t/y contained lithium. A source-reported grade or assay changes the conversion and must travel with the number.
Why capacity tables keep the source basis
A carbonate plant, a hydroxide plant, and a mine can each publish the same headline number while describing different quantities. The hub therefore shows raw source units first. Its optional LCE view displays the source value beside each derived value and names the registry version.
Unspecified hydroxide hydration, an unknown material identity, or an assay-free variable-grade feed cannot be converted. Those records remain visible, but their unresolved quantities stay outside totals.