There is hereby imposed upon semitaconite and semitaconite deposits, and upon the mining and quarrying thereof, and upon the production of concentrate or equivalent therefrom, and upon the concentrate or equivalent so produced, a tax of (a) in the case of concentrates agglomerated or sintered in Minnesota or to be agglomerated or sintered in Minnesota, five cents per gross ton of merchantable concentrate as produced therefrom, plus one-tenth of one cent per gross ton for each one percent that the iron content of such product exceeds 55 percent, when dried at 212 degrees Fahrenheit, or (b) in the case of all other concentrates or equivalent ten cents per gross ton of merchantable concentrate or equivalent as produced therefrom, plus one-tenth of one cent per gross ton for each one-half percent that the iron content of such product exceeds 55 percent, when dried at 212 degrees Fahrenheit. If any part of the ore materials from a semitaconite deposit, beneficiated in connection with or incidental to the beneficiation of semitaconite therefrom, is made merchantable by simple methods of beneficiation referred to in section 298.34, the tax hereunder upon the portion of merchantable concentrate so beneficiated shall be at the rate of ten cents per gross ton plus one-tenth of one cent per gross ton for each one-half of one percent that the iron content of such product exceeds 55 percent, when dried at 212 degrees Fahrenheit.