“post–1973 gold mine” means an independent workable proposition in respect of which the State President or the Minister of Mines has, after 1 January, 1974, on the recommendation of the Mining Leases Board signified in writing his decision to grant a lease of the right to mine for gold, and includes any other gold mine which, in the opinion of the Government Mining Engineer, is an independent workable proposition which was established as such after the said date;