Open-pit mining, also known as open-cast mining and open-cut 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).
Our open pit sulfur mine in eastern Sri Lanka is one of the worlds most ecologically friendly. All mine tailings are returned to the pit for later re-mining as the technology improves.