High-Purity Unwrought Magnesium (≥99.8% Mg)

A certified mill certificate or chemical analysis report from an accredited laboratory, specifying the magnesium content and listing all impurity elements, is the standard supporting document. CBP may request this at entry to verify the classification boundary. If the analysis shows magnesium content below 99.8%, the material would be classified under the subheading covering other unwrought magnesium, with potentially different duty treatment.

Alloy-grade magnesium (typically 99.5–99.7% Mg) is the workhorse material for die-casting and structural applications, where alloying elements like aluminum and zinc are intentionally added downstream. High-purity magnesium at 99.8%+ is required where those trace elements would cause problems — for example, in Grignard reagent synthesis, in nuclear applications, or as a reducing agent in titanium sponge production. Buyers in these sectors must specify and verify the purity grade, as the two products are not interchangeable despite similar physical appearance.