Surface mining is a type of
mining in which soil and rock overlying the mineral deposit are removed. It is the opposite of
underground mining, in which the overlying rock is left in place, and the mineral removed through shafts or tunnels. Surface mining is used when deposits of commercially useful
minerals or
rock are found near the surface; that is, where the overburden (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunneling (as would usually be the case for
sand,
cinder, and
gravel). Where minerals occur deep below the surface—where the overburden is thick or the mineral occurs as veins in hard rock— underground mining methods are used to extract the valued material. Surface mines are typically enlarged until either the mineral deposit is exhausted, or the cost of removing larger volumes of overburden makes further mining uneconomic.
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