Fluorine is the canonical example of an element traded entirely as a compound. Elemental F2 is too reactive to ship; the commercial stream begins with fluorspar (CaF2) mined as a concentrate, reacted with sulfuric acid to make HF, and from there branching into fluorochemicals, aluminum smelting flux, and uranium enrichment. Any schema that tries to express "F production" in tonnes of elemental F will silently misrepresent the industry — the production figures reported by USGS, BGS, and IEA are all CaF2 tonnage, not F tonnage.