Open pit mining commonly disturbs more land surface and earth
material than underground mining. The leading mines in the world are
open pit mines. The open pit mining process includes blasting the ore
loose, hauling it to a crusher, and breaking it into pieces small enough
for milling (Fig. 3). Technology has evolved to handle tremendous
volumes of material in this highly mechanized process of open pit
mining. Mines like the one shown on these pages produce up to
150,000 tons (136,000 tonnes) of ore daily. Typically, for every ton
of metal ore produced, as much as two or three tons
of waste rock are also produced. As mining operations expose the orebody, the mine geologist will
continue to map and describe it to ensure that the
most cost-effective mining plan is developed and
implemented.
Waste rock, the name for rocks and minerals
that enclose the ore and need to be removed
in order to recover it, contains too few valuable minerals to process. Although the metal
content of waste rock is too low to be recovered profitably, the environmental issues related
to its characteristics and handling are very important.
Large volumes of waste rock are created during the open pit mining
process. For example, the waste rock disposal areas that develop at a
surface mine like the Bingham Canyon mine sometimes cover hundreds
or even thousands of acres (tens of km2) and may be several hundred