1. - This appeal is directed against the judgment of learned Single Judge dated 21.11.2005 allowing the writ petition filed by the respondent company and relates to interpretation of the relevant entry made in Second Schedule annexed to Mines and Mineral (Development & Regulation) Act, 1957 (hereinafter referred to as 'the Act of 1957') providing for rates of royalty payable on Lead and Zinc as substituted vide notification dated 12.9.2000, and rules made for the purpose of determination of total royalty payable in respect of any mineral and the manner, time and place at which royalty is payable. The respondent company was originally incorporated for giving effect to aims and objects of The processing the run Metal Corporation of India (Acquisition of Undertaking) Act, 1966. One of the objects of the acquisition of Metal Corporation, which was first acquired by the Central Government in terms of Act of 1966, which in turn was repealed on enactment of The Metal Corporation (Nationalisation & Miscellaneous Provisions) Act, 1976 was to exploit to the fullest extent possible, the Zinc and Lead deposits in and around Zawar area in State of Rajasthan and to utilise those minerals in such manner as to subserve the common good, and for matters connected thereto.It is in the aforesaid background, the Hindustan Zinc Ltd. was granted mining lease for Zinc and Lead at Rajpura in District Rajsamand, Agucha Mines in District Bhilwara and Zawar Mines in District Udaipur. The lead and zinc are usually not found independently but are found in association with other minerals contained in the run of mines produced through mining operations. The Company had set up the processing plant within the mining lease area in order to obtain zinc concentrate and lead concentrate form run of mine and only after processing the run of mine, the concentrate were removed from the leased area for sale and use. Tailings left after processing the run of mine was a waste material, which was not usable in the sense that no zinc and lead was recoverable from it and was removed for dumping at a dumping place authorised for that purpose.Though under the Rajasthan Land Revenue Act, all minerals embedded in the earth vest in the State, the Parliament enacted the Mines and Mineral (Development & Regulation) Act, 1957 to provide for the development and regulation of mines and minerals under the control of Union. Entry 54 in the Union List of the Seventh Schedule legislative field for enacting laws on the subject of regulation of mines and minerals to the extent to which such regulation and development under the control of the Union is declared by Parliament by law to be expedient in the public interest is exclusive preserve of Parliament. It is with reference to aforesaid entry that Act of 1957 was enacted by Parliament, any provisions made under the Act of 1957 and Rules framed thereunder, the field was occupied by the Central Legislation and any provision made by the State with reference to Entry 23 of the State List of Seventh Schedule about regulation of mines and minerals development, to the extent it was repugnant to law, governed by law made in terms of Entry 57 of List-I became inoperative.Be that as it may, under the Act of 1957, Section 9 provides for Royalties in respect of mining leases. It inter alia provided that holder of mining lease shall pay royalty in respect of mineral removed or consumed by him or by his agent, manager, employee, contractor or sub- lessee form the leased area at the rate for the time being specified in the Second Schedule in respect of that mineral.Sub-section (3) of Section 9 enabled the Central Government to enhance or reduce the rate at which royalty shall be payable in respect of any mineral by a notification published in official gazette w.e.f. such date as may be specified in the notification subject to rider that Central Government shall not enhance the rate of royalty in respect of any mineral more than once during any