Page 656 - Environment: The Science Behind the Stories

978 lbs. We process metals after mining ore
Copper 27,471 lbs.
1.77 Troy oz. Salt Extracting minerals from the ground is the first step in putting
Gold them to use. However, most minerals need to be processed
11,994 lbs.
Clays in some way to become useful for our products. For exam-
16,306 lbs. ple, after ores are mined, the rock is crushed and pulverized,
Phosphate rock
521 lbs. and the desired metals are isolated by chemical or physical
Zinc
445,903 lbs. means. The material is then processed to purify the metals we
Coal desire. With coltan, processing facilities use acid solvents to
1.20 million lbs.
Stone, sand, and gravel separate tantalite from columbite. Other chemicals are then
6107 lbs. used to produce metallic tantalum powder. This powder can be
Bauxite
(Aluminum) 72,556 gallons consolidated by various melting techniques and can be shaped
Petroleum into wire, sheets, or other forms.
27,416 lbs. 840 lbs. Sometimes we mix, melt, and fuse a metal with another
Iron ore Lead metal or a nonmetal substance to form an alloy. For example,
steel is an alloy of the metal iron that has been fused with a
43,721 lbs. + 52,288 lbs.
Cement small quantity of carbon. The strength and malleability of this
6.63 million cu. ft. Other minerals particular alloy make steel ideal for its many applications in
Natural gas and metals
buildings, vehicles, appliances, and more. To make steel, we
Figure 23.2 At current rates of use, a baby born in 2012 is first mine iron ore, which consists of iron-containing com-
predicted to use over 1.3 million kg (3 million lb) of minerals pounds such as iron oxide. Steelmakers then heat the ore and
over his or her lifetime. Data from Minerals Education Coalition, 2013.
chemically extract the iron with carbon in a process known as
smelting (heating ore beyond its melting point and combining it
with other metals or chemicals). They then melt and reprocess
is lustrous, opaque, malleable, and can conduct heat and elec- the mixture, removing precise amounts of carbon and shaping
tricity. Most metals are not found in a pure state in Earth’s the product into rods, sheets, or wires. During this melting pro-
crust, but instead are present within ore, a mineral or grouping cess, certain other metals may be added to modify the strength,
of minerals from which we extract metals. malleability, or other characteristics of the steel, as desired.
Copper, iron, lead, gold, and aluminum are among the Processing minerals exerts environmental impacts. Most
many economically valuable metals we extract from mined methods are water-intensive and energy-intensive. Moreo-
ore. These metals and others serve so many purposes that ver, many chemical reactions and heating processes used
our modern lives would be impossible without them. The for extracting metals from ore emit air pollution, and smelt-
tantalum used in the electronic components of computers, ing plants in particular have long been hotspots of toxic air
cell phones, video game consoles, and other devices, as you pollution (Chapter 17). In addition, soil and water commonly
may recall from the case study, is a metal that comes from become polluted by tailings, portions of ore left over after
the mineral tantalite (Figure 23.3). In nature, tantalite is often metals have been extracted. Tailings may leach heavy met-
found with the mineral columbite within the ore called col- als present in the ore waste as well as chemicals applied in
tan. Columbite also contains the metal niobium, formerly the extraction process. For instance, we use cyanide to extract
known as columbium, which is utilized in ways similar to gold from ore, and we use sulfuric acid to extract copper.
tantalum. Mining operations often pump a toxic slurry of tailings into

Figure 23.3 Tantalum is used to manufacture electronics. Coltan ore (a) is mined from the ground and
then processed to extract the pure metal tantalum. This metal is used in capacitors (b) and other electronic
components in computer chips, cell phones, and many other devices.

(a) Coltan ore (b) Capacitor containing tantalum CHAPTER 23 • Min ERA ls A nd Mining

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