The geologic evolution of the Earth controls the quantity and the very
uneven distribution of metal resources in the Earth’s crust. Discovering
metal-rich deposits commonly requires extensive searching, and
exploration is the the first step in the mining cycle. Once exploration
geologists find an area with metals, they determine whether it is of
sufficient size and richness to be mined profitably. If the deposit is rich
enough, activities to extract the metals from the Earth begin.
Extraction, the next part of the cycle, involves mining to remove the
metal-bearing minerals from the Earth, mineral processing (beneficiation) to concentrate the metal bearing minerals, and smelting to liberate
metals from the minerals that contain them. Although beneficiation
and smelting are the most common processes, other processes such
as chemical leaching are used for some types of metal extraction.
Mine closure is the final step in the mining cycle. Mining eventually
depletes the metal-rich material that could be economically removed at
a specific mine. When mining can no longer be profitably conducted,
the mine and related facilities used in beneficiation or smelting will be
closed. Closure involves many activities specifically conducted to
prevent or mitigate undesired environmental and social impacts.
These activities involve reclaiming disturbed areas, removing facilities,
mitigating safety hazards, cross-training employees, and other activities
that lead to environmentally benign and safe conditions where mining
once took place.
Mining in the early days took place at a time when environmental
impacts were not as well understood and most importantly, not a
matter of significant concern. During these times, primarily before the
1970s, the mining cycle did not necessarily include closure activities
specifically designed to mitigate environmental or social impacts. As a
result, historical mine sites may still have unreclaimed areas, remnants
of facilities, and untreated water. This inherited legacy of environmental damage from mining is not indicative of the mining cycle today.
Now, mine closure and a number of activities to mitigate the social
and environmental impacts of mining are an integral part of all metal
mine planning and mineral development from the discovery phase
through to closure.