Customs classification of polymetallic concentrates is typically determined by the predominant metal by value or weight, following the HTS General Rules of Interpretation. When two metals are present in commercially significant quantities, importers should obtain a binding ruling from CBP to confirm the correct heading, as misclassification can result in underpayment of duties or incorrect trade remedy exposure.

Lead and zinc sulfide concentrates are classified as hazardous materials under DOT and IMDG (International Maritime Dangerous Goods) regulations due to their potential to self-heat and emit toxic gases in confined spaces. Shippers must comply with proper packaging, labeling, and stowage requirements, and vessels carrying bulk sulfide concentrates must follow IMSBC Code provisions for Group B materials.