mining engineering 335 history 87 ore deposits 34 uranium 26 mineral deposits 24 crude oil 21 coal 20 more ... natural gas 20 silver 19 deep mining 17 hard coal 15 metallurgy 14 mining 14 brown coal 13 ores 13 deposits mining 12 geological survey 11 mining law 10 environment protection 9 gold 9 metallography 8 environment 8 safety of work 7 mine exploitation 7 economy 7 lead 7 environmental pollution 7 mineral processing 7 business balance sheet 6 mines (mining) 6 less ...