(1) There is hereby levied an excise tax upon every person engaging in the business of severing heavy minerals from the soils or waters of this state for commercial use. The tax shall be collected, administered, and enforced by the department. The proceeds of the tax imposed by this section shall be paid into the State Treasury as provided in s. 211.31(1) for certain solid minerals. (2) The excise tax levied by this section shall apply to the total production of the producer during the taxable year, measured on the basis of bone-dry tons of heavy minerals severed for commercial use at the point of severance, subject to the following rate: Beginning July 1, 1997, and thereafter, the tax rate shall be the base rate of $1.34 per ton severed times the base rate adjustment for the tax year as calculated by the department in accordance with subsection (3).
(3)(a) On or before March 30, 1982, and annually thereafter, the department shall calculate the base rate adjustment, if any, for heavy minerals based on the change in the 5-year moving average of the annual producer price indexes for titanium dioxide in relation to the base period.
(b) For the purposes of determining the base rate adjustment for any year, the base rate adjustment shall be a fraction, the numerator of which is the average of the annual producer price indexes for titanium dioxide for the period and the denominator of which is the average of the annual producer price indexes for titanium dioxide for the base period.
(c) The department shall provide the base rate, the base rate adjustment, and the resulting tax rate to affected producers by written notice on or before April 15 of the current year.
(d) If the producer price index for titanium dioxide is substantially revised, or if the base year used as an index of 100 is changed, the department shall make appropriate adjustment in the method used to compute the base rate adjustment under this subsection, which will produce results reasonably consistent with the result which would have been obtained if the producer price index for titanium dioxide had not been revised or the base year changed.
(e) If the producer price index for titanium dioxide is discontinued or can no longer be calculated, a comparable index must be selected by the department and adopted by rule. If there is no comparable index, the tax rate for the immediately preceding year must be used.
(4) The excise tax levied on the severance of heavy minerals shall be in addition to any ad valorem taxes levied upon the separately assessed mineral interest in the real property upon which the site of severance is located, or any other tax, permit, or license fee imposed by the state or its political subdivisions.
(5) The tax levied by this section shall be collected in the manner prescribed in s. 211.33 and shall be expressly applicable for the severance of heavy minerals in the 1981 tax year. 
