All ores or concentrates shipped from the lands covered by any lease under section 93.20 shall be classified and paid for under and in accordance with the particular schedule of said law properly applicable thereto. The royalty provided for taconite concentrates in section 93.20, schedule 7, shall be applicable to concentrates produced from taconite ores which, in accordance with good engineering and metallurgical practice, require treatment by fine grinding, magnetic separation, flotation, or some other method or methods other than or in addition to one or more of the methods specified in schedules 1 to 6, inclusive, of said section to make them suitable for blast furnace use.
The provisions of subdivisions 1 and 2 for payment of royalty on taconite ore shall apply to existing leases as well as subsequent leases, subject to vested rights, if any, of the holders of existing leases.
Minn. Stat. § 93.201
1943 c 233 s 3; 1949 c 616 s 1,2; 1957 c 158 s 1; 1969 c 1129 art 10 s 2