The El Chino mine located near Silver City, New Mexico is an open-pit copper mine
Open-pit mining refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow. The term is used to differentiate this form of mining from extractive methods that require tunneling into the earth. Open-pit mines are 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 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—tunnels (mining with shafts) may be necessary to extract the valued material. Open-pit mines are typically enlarged until the mineral resource (or the plot of land owned by the mining company) is exhausted.
Open-pit mines that produce building materials are commonly referred to as quarries. People in some English-speaking countries are not likely to make a distinction between an open-pit mine and other types of open-cast mines, such as quarries, borrows, placers, and strip mines.
When they are no longer productive for extraction of material, open-pit mines are sometimes converted to landfills for disposal of solid wastes. However, some form of water control is usually required to keep the mine pit from becoming a lake.
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