Tex. Natural Resources Code § 71.009: ROYALTY.

(a) In each lease other than a lease for coal and lignite executed under this subchapter, the lessor shall retain at least a one-eighth royalty.

(b) In a lease for coal and lignite executed under this subchapter, the lessor shall retain at least a royalty based on one of the following or a combination of the following:

(1) a sum certain per ton;

(2) a percentage certain of the gross sale price F.O.B. at the mine site of the coal and lignite; or

(3) a sum certain for each acre-foot of coal and lignite mined and removed from the premises.

(c) Royalties under a coal and lignite lease may be paid as advanced mineral royalties.

Acts 1977, 65th Leg., p. 2505, ch. 871, art. I, Sec. 1, eff. Sept. 1, 1977.