… (witherite), whether or not calcined, other than barium oxide of heading 28.16. …
Explanatory notes
… (witherite), whether or not calcined, other than barium oxide of heading 28.16. 2511.10 ‑ Natural barium sulphate … naturally occurring barium sulphate (barytes ‑ sometimes known as heavy spar) and barium carbonate (witherite). … Calcined witherite, which consists largely of impure barium oxide, remains in this heading. The heading excludes …