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Science and Society

Costs of Mining Mineral Resources
ncient humans exploited mineral quantities of water for the extraction or an eyesore, and it is difficult for vegetation
A resources as they mined copper miner- concentration of a mineral resource. If to grow on the barren rock. Since plants are
als for the making of tools. They also used the energy and water are not readily avail- not present, water may wash away small rock
salt, clay, and other mineral materials for able, the resource cost might be converted particles, causing erosion of the land and
nutrients and pot making. These early peo- to economic cost, which could ultimately silting of the streams. The debris might also
ple were few in number, and their simple determine whether the operation will be contain arsenic, lead, and other minerals that
tools made little impact on the environ- profitable. Finally, the third category is the can pollute the water supply.
ment as they mined what they needed. As environmental cost of mining the resource. Today, regulations on the mining
the numbers of people grew and technology Environmental cost is converted to eco- industry require less environmental dam-
advanced, more and more mineral resources nomic cost as controls on pollution are age than had been previously tolerated.
were utilized to build machines and pro- enforced. It is expensive to clean pollution The cost of finding and processing the
vide energy. With advances in population from the land and to restore the ecosystem minerals is also increasing as the easiest
and technology came increasing impacts that was changed by mining operations. to use, less expensive resources have been
on the environment in both size and scope. Consideration of the conversion of environ- utilized first. As current mineral resource
In addition to copper minerals and clay, the mental cost to economic cost can also deter- deposits become exhausted, pressure will
metal ores of iron, chromium, aluminum, mine if a mining operation is feasible or not. increase to use the minerals in protected
nickel, tin, uranium, manganese, platinum, All mining operations start by mak- areas. The environmental costs for utiliza-
cobalt, zinc, and many others were now in ing a mineral resource accessible so it can tion of these areas will indeed be large.
high demand. be removed. This might take place by strip
Today, there are three categories of mining, which begins with the removal of QUESTIONS TO DISCUSS
costs recognized with the mining of any the top layers of soil and rock overlying a
mineral resource. The first category is the resource deposit. This overburden is placed Divide your group into three subgroups:
economic cost, the money needed to lease or somewhere else, to the side, so the mineral one representing economic cost; one,
buy land, acquire equipment, and pay for deposit can be easily removed. Access to a resource cost; and one, environmental
labor to run the equipment. The second cat- smaller, deeper mineral deposit might be cost. After a few minutes of preparation,
egory is the resource cost of mining. It takes gained by building a tunnel to the resource. have a short debate about the necessity
energy to concentrate the ore and trans- The debris from building such a tunnel is of having mineral resources at the lowest
port it to smelters or refineries. Sometimes usually piled outside the entrance. The rock cost possible versus the need to protect our
other resources are needed, such as large debris from both strip and tunnel mining is environment no matter what the cost.

Igneous rocks on the right side of the chart usually have a
greater density than rocks with the granite chemical composition, SOLUTION
and they are very dark in color. The most common example of Read the percentage associated with the range of each mineral in
these dark, relatively high-density igneous rocks is basalt. Basalt granite from Figure 17.13 and calculate the difference to determine
is the dark, fine-grained igneous rock that you probably associate the percentage of each mineral at each boundary of the range in
composition.
with cooled and hardened lava. Basalt is fine-grained, so you can-
not see any mineral particles, and a freshly broken surface looks Granite (high silica boundary)
sugary. As shown in the chart, basalt is about one-half plagioclase Biotite 100% − 95% = 5%
feldspars and about one-half ferromagnesian minerals. Sodium-rich plagioclase 95% − 85% = 10%
Basaltic rocks, meaning rocks with the chemical composi- Potassium feldspar 85% − 32% = 53%
tion of basalt, make up the ocean basins and much of Earth’s Quartz 32% − 0% = 32%
interior. Basalt is the most common extrusive rock found on
Granite (low silica boundary)
Earth’s surface. The coarse-grained chemical equivalent of ba-
Biotite 100% − 70% = 30%
salt is called gabbro.
Sodium-rich plagioclase 70% − 0% = 70%
Potassium feldspar 0% − 0% = 0%
EXAMPLE 17.3 Quartz 0% − 0% = 0%
Igneous rock classification is based on the proportion of the minerals Range
present in the rock as shown in the fields containing the mineral names Biotite 5% to 30%
in Figure 17.13. For a given igneous rock name, this proportion varies
based on the silica content, and it is read from the percentages on the Sodium-rich plagioclase 10% to 70%
y axis of the chart. Based on Figure 17.13, what is the range in percent- Potassium feldspar 0% to 53%
age of each mineral in granite? Quartz 0% to 32%

17-11 CHAPTER 17 Rocks and Minerals 443