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.