As used in this chapter “mineral leasing laws” shall mean the Act of October 20, 1914 (38 Stat. 741); the Act of February 25, 1920 (41 Stat. 437) [30 U.S.C. 181 et seq.]; the Act of April 17, 1926 (44 Stat. 301) [30 U.S.C. 271 et seq.]; the Act of February 7, 1927 (44 Stat. 1057) [30 U.S.C. 281 et seq.]; and all Acts heretofore or hereafter enacted which are amendatory of or supplementary to any of the foregoing Acts; “Leasing Act minerals” shall mean all minerals which, upon August 11, 1955, are provided in the mineral leasing laws to be disposed of thereunder; “lignite” shall mean coal classified as ASTM designation: D 388–38, according to the standards established in the American Society for Testing Materials on Coal and Coke under standard specifications for Classification of Coals by Rank, contained in public-land deposits considered as valuable under the coal-land classification standards established by the Secretary of the Interior and prescribed in section 30, Code of Federal Regulations, part 201; and “source material” shall mean uranium, thorium, or any other material which is determined by the Atomic Energy Commission pursuant to the provisions of section 2091 of title 42 to be source material.