The state shall have the right to sell or otherwise dispose of any timber, stone, or other valuable materials, except coal, found upon the land during the period covered by any option contract, or lease issued under the foregoing provisions, with the right to enter upon such lands and cut and remove the same, and shall not be obliged to withhold from sale any timber for coal mining or prospecting purposes. However, the lessee shall be permitted to use in mining operations any timber found upon the land, first paying therefor to the department the value thereof as fixed by the department. Further, any bill of sale for the removal of timber, stone, or other material given subsequent to the coal lease shall contain provisions preventing any interference with the operations of the coal lease.