Classification follows the essential character of the concentrate. If silver is the predominant precious metal by value or content, 261610 applies; if gold or a platinum-group metal predominates, 261690 is the correct heading. When the composition is ambiguous, a binding ruling from CBP is advisable given the high unit values involved.

Importers generally need a commercial invoice with detailed assay results (metal content by weight), a certificate of origin, and a packing list. High-value shipments may also require a surety bond. Depending on the refinery destination and metal type, FinCEN anti-money-laundering reporting obligations and state-level precious-metals dealer regulations may also apply.