Figure 4 illustrates the underground mining process. Underground
mines may use vertical shafts as shown, or mine openings driven
into mountainsides, known as “adits.” Although the primary
challenge for underground and open pit mining is the same —
to remove ore economically from the enclosing rocks — underground mining differs in two important ways.
First, the size of the operation is much smaller than in open pit mining,
and the mining activities are not as visible at the surface. Figure 5
shows examples of relatively large underground openings and
related mining equipment. Over the life of
an underground mine, the volume
of ore produced is most commonly only a few hundred
thousand to a few million tons. This compares to production
at larger open pit
mines where one
million tons of ore
may be produced
in just one week
of operations.