( 1 ) THE Gujarat State Legislature enacted the Gujarat Mineral Rights Tax Act 1985 (Gujarat Act 19 of 1985) (hereinafter referred to as the impugned Act or the impugned Legislation) to provide for the levy and collection of tax on mineral rights of holders of mining leases in respect of certain minerals in the State of Gujarat specified in the Schedule. The Act received the assent of the Governor of Gujarat on 2/08/1985 and was first published in the Gujarat Government Gazette on 3/08/1985 By a notification dated 29/10/1985 issued under sub-sec. (3) of Sec. 1 the State Government brought the Act into force with effect from 1/11/1985

( 2 ) THE petitioners of this group of Writ Petitions are holders of mining leases granted by the State of Gujarat under provisions of the Mines and Minerals (Regulation and Development) Act 1957 (Central Act 67 of 1957) (hereinafter called the Central Act) read with the Concession Rules 1960 Under the terms of the lease deed specimen copy whereof is produced at Annexure B in Special Civil Application No. 2298 of 1986 the petitioners have a right to mine limestone and/or calcarious sand from the leased area. The indenture of lease Annexu