Extraction of Materials from Earth

The extraction of minerals from placer deposits formed by deposition from water has obvious environmental implications. Placer deposits can be mined by dredging from a boom-equipped barge. Another means that can be used is hydraulic mining with large streams of water. One interesting approach for more coherent deposits is to cut the ore with intense water jets and then suck up the resulting small particles with a pumping system. 

For many minerals, underground mining is the only practical means of extraction. An underground mine can be very complex and sophisticated. The structure of the mine depends on the nature of the deposit. It is of course necessary to have a shaft that reaches to the ore deposit. Horizontal tunnels extend out into the deposit, and provision must be made for sumps to remove water and for 

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