Section 16(1)(a) in The Mines And Minerals (Development And Regulation) Act, 1957
(a)All mining leases granted before the commencement of the Mines and Minerals (Regulation and Development) Amendment Act, 1972, [Inserted by Act 37 of 1986, Section 13 (w.e.f. 10.2.1987). ][if in force at the date of commencement of the Mines and Minerals (Regulation and Development) Amendment Act, 1994, shall be brought in conformity with the provisions of this Act and the rules made thereunder within two years from the date of the commencement of the Mines and Minerals (Regulation and Development) Amendment Act, 1994] [ Substituted by Act 25 of 1994, Section 6, for certain words (w.r.e.f. 25.1.1994).][, or such further time as the Central Government may, by general or special order, specify in this behalf.