mining engineering 322 history 89 ore deposits 34 uranium 26 coal 23 mineral deposits 19 silver 19 more ... deep mining 18 hard coal 16 brown coal 15 metallurgy 14 mining 14 ores 13 deposits mining 12 natural gas 12 mining law 11 geological survey 10 environment protection 9 gold 9 caustobiolite deposits 8 metallography 8 environment 8 safety of work 7 mines (mining) 7 mine exploitation 7 economy 7 lead 7 environmental pollution 7 coal energy sources 6 metals 6 less ...