Buyers must distinguish between Technical Grade, Agricultural Grade, and Pharmaceutical/Food Grade (USP/BP/FCC). For personal care or food applications, ensure a purity level of ≥99.5%. Key chemical markers include Magnesium (Mg) content (typically ~9.8%) and Magnesium Sulfate (MgSO4) content (≥48% for heptahydrate). Pay close attention to particle size (granularity), ranging from extra fine to large crystals, depending on whether it is for rapid dissolution in baths or slow-release in fertilizers.