Mining - Underground mining | Britannica.com

Mining - Underground mining: When any ore body lies a considerable distance below the surface, the amount of waste that has to be removed in order to uncover the ore through surface mining becomes prohibitive, and underground techniques must be considered. Counting against underground mining are the costs, which, for each ton of material mined, are much higher underground than on the surface.

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Gold Bars Worldwide was established in 2007 to support the promotion of gold worldwide. Although no longer updated, it remains an important source of information on widely-traded gold bars and the world's leading gold refiners.

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