Texas Natural Resources Code - NAT RES § 53.111. Authority to Operate an Area as a Unit for Production of Sulphur

(1) the royalty interests in sulphur reserved to the state or any fund of the state by law in a patent, award, mining claim, or contract of sale or under the terms of any lease legally executed by an official, board, agent, agency, or authority of the state;  or

(2) the free royalty interests, whether leased or unleased, reserved to the state under Section 51.201 or 51.054 of this code.