V. P. TYAGI, J.

( 1 ) ALL the three petitioner companies in these three separate writ petitions are quarrying lime-stone from the areas leased out to them and therefore all of them have challenged the validity of the notification dated 29th January, 1970, issued by the Union of India whereby item No. 8 in the Second Schedule of the Mines and minerals (Regulation and Development) Act, 1957 (hereinafter called the Act) has been amended. Since common questions of law are raised in all these petitions, I propose to dispose them of by one judgment.

( 2 ) PETITIONER companies have been holding areas in their respective fields of operation under the mining lease granted to them for quarrying limestone. The contention of the petitioners is that the limestone quarried by each one of them is of inferior grade with less than 45% calcium oxide. Section 9 of the Act lays down that the holder of a mining lease shall pay royalty on the mineral in accordance with the rates for the time being specified in the Second Schedule in respect of that mineral. Sub-section (3) of this section empowers the Central Government to amend the Second Schedule by issuing a notification so as to enhance or