Minn. Stat. § 298.393

There is hereby imposed upon agglomerating facilities and upon the production of agglomerates and other merchantable iron ore products therein and upon the agglomerates and other products so produced, a tax equal to five cents per gross ton of agglomerates and other merchantable iron ore products which shall have been produced in the agglomerating facility during the calendar year plus one-tenth of one cent per gross ton for each one percent that the iron content of such products exceeds 55 percent, when dried at 212 degrees Fahrenheit.