Roasting is the processing step that distinguishes this heading from its unroasted counterpart: calcining molybdenite concentrate converts it to molybdic oxide (MoO₃), the intermediate form preferred by steel alloy and chemical producers. Mexico and Chile are the leading US suppliers, consistent with their roles as major copper-molybdenum porphyry mining nations where moly is recovered as a byproduct. Because roasted concentrate is a higher-value, further-processed product, importers should verify that the roasting step was completed prior to export to support classification here rather than under the unroasted heading.

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