Open-pit mining

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). For minerals that occur deep below the surface—where the overburden is thick or the mineral occurs as veins in hard rock— underground mining methods extract the valued material.

Open-pit mines that produce building materials and dimension stone are commonly referred to as quarries. People are unlikely to make a distinction between an open-pit mine and other types of open-cast mines,[citation needed] such as quarries, borrows, placers, and strip mines.