Tyler Shiflett
Chapter 16-Minerals: A Nonrenewable Resource
The General Mining Law of 1872- was established to encourage settlement in the
sparsely populated western states. It allows companies or individuals to stake mining
claims on federal land. They then purchase the land for $2.50-$5.00 an acre in order to
extract hardrock minerals such as gold, silver, copper, lead, or zinc. These miners are
able to keep all of the profits.
- no provisons for environmental protection
Minerals- Elements or compounds of elements that occur naturally in the Earth’s
crust.
- Minerals are essential in human life
- Ex. Steel, aluminum, copper, limestone, sulfur, platinum, mercury,
manganese, and titanium
- Sulfides: mineral compounds in which certain elements are combined
chemically with sulfir
- Oxides: mineral compounds in which elements are combined chemically with
oxygen
- Rocks: naturally formed aggregates, or mixtures of minerals and have varied
chemical compositions
- Ore: rock that contains relatively large amounts of profitable minerals. Lowgrade ores have lesser amount of these minerals and high- grade ores are the
opposite.
Metallic and Nonmetallic Letters
o Metals: minerals such as iron, aluminum, and copper, which are
malleable, lustrous, and good conductors of heat and electricity.
o Nonmetallic minerals such as sand, stone, salt, and phosphates lack
these characteristics.
Formation of Mineral Deposits
- Magmatic Concentration: Magma cools and solidifies deep in Earth’s crust
where it often separates into layers, with the heavier iron- and magnesiumcontaining rock settling on the bottom and the lighter silicates rising to the
top. Varying concentrations of minerals are often found in different rock
layers.
- Hydrothermal Processes: Water that was heated deep in Earth’s crust seeps
through cracks and fissures and dissolves certain minerals in the rocks. The
minerals are then carried along in the hot water solution. The dissolving
ability of water is greater if chlorine or fluorine is present because these
elements react with many metals to form salts that are soluble in water. When
the hot solution encounters sulfur, a chemical reaction between the metal salts
and the sulfur produces metal sulfides. These sulfides are not soluble in water,
so they form deposits by settling out of the solution. Gold, silver, lead, and
zinc are products of this process.
- Sedimentation: Weathered rock particles are transported by water and
deposited as sediment on riverbanks, deltas, and the sea floor. During
transport, certain minerals in the weathered particles dissolve in the water,
and later settle out of the solution. When warm river water meets cold ocean
water, settling occurs because less material deposits dissolve in cold water than
in warm water.
- Evaporation: When significant amounts of dissolved material accumulate in
inland lakes or seas that have no outlet or only a small outlet to the ocean.
When the water is dried up, a large amount of salt is left behind.
Discovering Mineral Deposits
- Aerial or satellite photography
- Aircraft and satellite instruments that measure earths magnetic field and
gravity
- Seismographs used to detect earthquakes
- Deposits on the ocean floor are discovered by three dimensional maps of the
sea floor and the use of depth- measuring devices
Extracting Minerals
- Surface mining: the extraction of mineral and energy resources near Earth’s
surface by first removing the soil, subsoil and overlying rock strata.
1. Open- pit surface mining: a giant hole is dug. Large holes that are
formed are called quarries.
2. Strip mining: a trench is dug to extract minerals. Then a new trench
is dug parallel to the old one. The overburden from the new
trench is put in the old trench creating a spoil bank.
3. Spoil bank: a hill of loose rock created when the overburden from a
new trench is put into the already excavated trench during strip
mining.
- Subsurface mining: the extraction of mineral and energy resources from deep
underground deposits. Disturbs land less but is expensive and more hazardous
for miners.
1. Shaft mine: a direct vertical shaft to the vein of ore. The ore is
broken up underground and then hoisted through the shaft to the
surface in buckets.
2. Slope mine: has a slanting passage that makes it possible to haul the
broken ore out of the mine in cars rather than hoisting it up in
buckets. Sump pumps keep the subsurface mine dry, and a second
shaft is usually installed for ventilation.
- Overburden: soil and rock overlying a useful mineral deposit
Processing Minerals
- Often involves smelting, or the process in which ore is melted at a high
temperature to separate impurities from the molten metal. This pollutes air
soil and water.
Mining and the Environment
- Mining disturbs large areas of land because mining destroys vegetation, so it is
prone to erosion. Wind erosion causes air pollution and water erosion pollutes
nearby waterways and damages aquatic habitats.
- Open-pit mining uses huge quantities of water. When miners hit the water
table, they must pump out the water to keep the pit dry. Environmentalists
and others would like miners to reinject the water into the ground after they
have pumped it out.
- Mining affects water quality. Rocks rich in minerals often contain high
concentrations of heavy metals. Rainwater can seep through sulfide minerals
in mine wastes, which produces sulfuric acid, which in turn dissolves into other
toxic substances. This is called acid mine drainage when the toxins make their
way to nearby lakes and streams.
- Before mining it is suggested that companies conduct a cost-benefit analysis
that includes the benefits of the mine in dollar terms versus the benefits in
dollar terms of preserving the land intact for wildlife habitat, indigenous
people, watershed protection, and recreation.
- About 80% or more of mined ore consists of impurities that become wastes
after processing. These wastes, or tailings, are usually left in giant piles on the
ground or in ponds near the processing plants. The toxic tailings contaminate
the air, soil, and water.
- Smelting plants can emit large quantities of air pollutants during mineral
processing. Unless pollution-control devices are added to smelters, the sulfur it
produces escapes into the atmosphere to form sulfuric acid. Additionally,
smelters emit hazardous liquid and solid wastes that can cause soil and water
pollution.
- One huge problem for the environment is that it takes a large amount of
energy to mine and refine minerals, particularly if they are being refined form
low-grade ore.
Restoration of Mining Lands:
- Land can be reclaimed or restored when the mine is no longer profitable to
operate. Goals: prevent further degradation and erosion of the land, eliminate
or neutralize local sources of toxic pollutants, and make the land productive
for purposes other than mining.
- Lands destroyed by mining are called derelict lands. After grading the derelict
land, plants that can tolerate the toxins in the soil must be planted.
- The Surface Mining Control and Reclamation Act of 1977: requires
reclamation of areas that were surface mined for coal.
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Wetlands can be established to trap sediments and pollutants, so water quality
of downstream areas is improved. A series of wetlands is the most effective
way to clean up this area. However, artificial wetlands take 50 to 100 years to
neutralize acid enough for life to return to water sources downstream form acid
mine damage.
Dumping cow manure onto mining lands causes the pH of the mine drainage
water to increase as bacteria consume the manure.
Phytoremediation- the use of specific plants to absorb and accumulate toxic
materials such as nickel from the soil. The nickel can then be taken from the
plants’ ashes after they are burned and it can be reused.
Distribution vs. Consumption
-
Mineral Reserves: Mineral deposits that have been identified and are currently
profitable to extract.
Mineral Resources: Any undiscovered mineral deposits or known deposits of
low-grade ore that are currently unprofitable to extract but maybe profitable
later.
The combination of a mineral’s reserves and resources is its total resources or
world reserve base.
Most experts think mineral supplies, both metallic and nonmetallic, will be
adequate during the 21st century. Additionally, they think that prices of even
relatively plentiful minerals will increase.
Minerals in Antarctica
- The Antarctic Treaty: limits activity in Antarctica to peaceful uses such as
scientific studies, since no one owns Antarctica.
- The Environmental Protection Protocol to the Antarctic Treaty or the Madrid
Protocol was established in 1990, and it designates Antarctica and its marine
ecosystem as a “natural reserve dedicated to peace and society.”
Minerals from the Ocean
- Minerals could be extracted from seawater, or the sea floor may be mined
where minerals have accumulated in the loose ocean sediments or near
underwater volcanoes.
- Seawater contains many different dissolved materials, but they are of a very
low concentration.
- The U.N. Convention on the Law of the Sea (UNCLOS), which became
effective in 1994, is generally considered a constitution for the ocean that
protects its resources. The provisions of UNCLOS are not binding for
territorial waters, only for international waters, so there is no legal reason to
block seabed mining. Seabed miners acknowledge that some organisms will die
during the mining process.
- Manganese nodules: small rocks the size of potatoes that contain manganese
and other minerals
Advanced Mining and Processing Technologies
- Biomining: the idea to use microorganisms to extract minerals form low-grade
ores.
Finding Mineral Substitutes
- Economics partly drive the search for substitutes because they are one way to
cut production costs. It is cheaper to substitute an abundant material for an
expensive or scarce one.
Mineral Conservation
- Reuse (conservation of resources in used items by using them over and over
again) is one way to extend mineral resources. This type of conservation
reduces mineral consumption and pollution. Reusing a product expends less
energy than recycling it. Reuse also reduces litter and solid waste.
- Recycling: used items can be conserved by being converted into a new product.
Recycling saves unspoiled land from the disruption of mining, reduces the
amount of solid waste that must be disposed, and decreases energy
consumption and pollution. It takes approximately six weeks for a used can to
be melted, re-formed, filled, and put back on a supermarket shelf.
- Dematerialization: is the decrease in weight of products over time. However,
smaller and lighter products may be of lower quality. Although the weight of
materials being used to make each item has decreased, the number of such
items being used in a given period may have actually increased.
- Sustainable manufacturing: a manufacturing system based on industrial waste
minimization