For the purpose of this section, ores usable as a flux or sulphur reagent, mentioned in the provision for such ores in subheading 2603.00.00, Harmonized Tariff Schedule of the United States, shall include only ores which contain by weight not over 15 percent copper.

[Reserved]

There shall be filed in connection with the entry of such copper-bearing ores, either for consumption or warehouse, a declaration of the importer, or its electronic equivalent, that the material is to be used for fluxing purposes only. In the case of a consumption entry, the estimated tax shall be deposited at the time of entry. Liquidation of entries shall be suspended pending proof of use for fluxing purposes as hereinafter provided.

Samples of the material shall be taken in accordance with the commercial method in effect at the plant if to be used in a bonded smelting warehouse, or in accordance with §§ 151.52 through 151.55 of this chapter if entered for consumption, and the copper content thereof shall be determined by the Government chemist in accordance with the assay.

The management of the smelting or converting plant shall file with the appropriate Customs officer at the port or ports where the entries are to be liquidated, a statement based on its records of operation for each quarterly period showing for each furnace or converter the total quantity of material charged during each month or part thereof of each quarter, the total quantity of material used for fluxing purposes, and the quantity of imported ores used for fluxing purposes for which free entry was claimed under the above-mentioned provision, together with the copper content of such imported ores computed in accordance with the Government assay. If the quantity of ores used for fluxing purposes in any furnace or converter during any month or part thereof of any quarter is in excess of 25 percent of the charge of such furnace or converter, the quarterly statement shall be accompanied by an explanation of the necessity for using such quantity for fluxing purposes.