mining engineering 331 history 86 ore deposits 34 uranium 26 mineral deposits 23 coal 22 crude oil 21 more ... natural gas 19 deep mining 18 silver 16 brown coal 14 metallurgy 14 mining 14 hard coal 14 ores 13 geological survey 11 mining law 10 gold 9 caustobiolite deposits 8 metallography 8 environment protection 8 environment 8 mines (mining) 7 economy 7 lead 7 environmental pollution 7 safety of work 6 business balance sheet 6 mine exploitation 6 coal energy sources 6 less ...