China controls a large share of global magnesite reserves and processing capacity, meaning US buyers of natural magnesium carbonate are heavily exposed to Chinese export policy, environmental production restrictions, and any trade-remedy measures that may apply. Importers sourcing from China should monitor Section 301 tariff applicability and consider qualifying alternative suppliers in Brazil or India as contingency sources.

Natural magnesite is the unprocessed or simply crushed/ground mineral as it occurs in nature. Once it is calcined or sintered to produce magnesium oxide (magnesia), it moves to heading 2519 subheadings covering fused magnesia, dead-burned magnesia, or caustic-calcined magnesite. The presence or absence of thermal processing is the definitive classification boundary.