Chapter 13: Mineral Resources and Mining. Lesson 1: Minerals and Rocks

Chapter 13: Mineral Resources and Mining

Lesson 1: Minerals and Rocks

—What are Minerals?o A mineral is a naturally occurring, inorganic solid

that has an orderly crystalline structure and a definite chemical composition.

o To be a mineral, a substance must be formed by processes within Earth, on the surface of Earth, or within organisms.

o Inorganic materials do not contain carbon-carbon and carbon-hydrogen bonds

o A crystalline structure occurs when atoms or ions are arranged in an orderly and repetitive manner. Each type of mineral has a unique crystal structure

oMost minerals are compounds made of two or more elements

—Mineral FormationoMinerals can form by crystallization from magma

or lava, from precipitation related to evaporation or hydrothermal solutions, from exposure to high pressure and temperature, or they can be produced by organisms.

oMagma is a molten mixture of substances that forms deep within Earth

oWhen magma emerges at Earth’s surface it is called lava

o As magma cools inside the crust or lava hardens on the surface, crystallization occurs and minerals can form Slow cooling of magma results in large crystals Fast cooling of lava results in small crystals

oMinerals form by precipitation when the liquid in a solution evaporates and the remaining solids crystallize.

o Polymorphs consist of the same elements or compounds, but have different crystal structures due to the conditions under which they formed. When a mineral is subjected to great changes in

temperature or pressure, its atoms may rearrange, causing it to become a different type of mineral

o Some organisms form inorganic minerals to produce hard structures that provide protection or support Ex: calcium carbonate in coral

—Rockso Forces deep inside and at the surface of Earth produce

changes in rock that cause the same material to cycle between igneous, sedimentary, and metamorphic rock stages.

o A rock is a solid mass of minerals and mineral-like material that occurs naturally.

o The rock cycle is a very slow process in which rocks are heated, melted, cooled, weathered, and eroded as they slowly change between the three different types of rock – igneous, sedimentary, and metamorphic.

o Igneous Rock Rock that forms as magma cools and solidifies is called

igneous rock When magma cools slowly well below the Earth’s

surface it forms intrusive igneous rock• Ex: granite

When lava cools quickly on the Earth’s surface it forms extrusive igneous rock• Ex: basalt

igneous rocks

o Sedimentary Rock As layers of sediment build up over time, the weight on the

earliest layers increases and compacts them. Dissolved minerals seep through sediment layers and over time the minerals crystallize and bind the sediment particles together.• Results in a clastic sedimentary rock

When water evaporates and leaves behind minerals and other materials, which crystallize together it forms chemical sedimentary rock

Remains of marine organisms that accumulate in an area and eventually bond together form biochemical sedimentary rock.• Ex: limestone

oMetamorphic Rock When rock is exposed to great heat or pressure, or

both, the rock may become metamorphic rock Common types include marble and soapstone

Lesson 2: Mining

—What is Mined?o Mining companies seek and gather valuable

resources such as metals, nonmetallic minerals, and fuel sources.

o Mining involves breaking into the ground to gain access to minerals, fossil fuels, or water, and extracting them.

o A mineral or group of minerals that is mined so that a metal or metals can be removed from it is called ore. Most are a mixture of materials

o Nonmetallic minerals may actually contain metal as a chemical component, but they are not mined for the metal.

o One of the most commonly mined fuels is coal.o Other fuels, such as petroleum, natural gas, oil

sands, and methane hydrates, as well as groundwater are also extracted from Earth.

—Mining MethodsoMining companies have developed many

techniques to access resources close to the surface of Earth, deep underground, and even underwater.

o Strip mining During strip mining, layers of surface soil and rock are

removed from large areas to expose the resource. Heavy machinery removes the soil and rock, extracts

the resource, and then replaces the soil and rock. Commonly used to mine coal, sand, and gravel.

o Subsurface mining In subsurface mining, vertical shafts are dug deep into

the ground, and networks of horizontal tunnels are dug or blasted out to follow deposits of the resource.

Miners remove the resource and transport it out of the mine

Used for zinc, lead, nickel, tin, gold, copper, uranium, diamonds, phosphate, and salt.

o Open Pit mining Involves digging a large hole and removing ore and the

unwanted rock that surrounds the ore Open pit mines are usually expanded until the resource

runs out or becomes so difficult to mine that it is unprofitable to continue.

Used for copper, iron, gold, diamonds, and coal. Similar methods are used to extract clay, gravel, sand,

limestone, granite, marble, and slate, but in these cases the pits are known as quarries.

oMountaintop Removal First the forests are clear cut and the timber is sold or

burned. Then the topsoil is removed and rock is blasted away to expose the resource.

Repeated cycles of blasting and extraction can eventually remove hundreds of vertical feet of mountaintop.

o Solution Mining Miners sometimes pump a chemical solution into a

mine to leach the desired resource from the ore Once the solution has reacted with the ore, the liquid is

removed from the mine, taking the resource with it Used in salt mines

o Placer Mining Involves sifting through material in modern or ancient

riverbed deposits• Usually use running water to separate the lightweight mud

and gravel from the heavier minerals Ex: California and Alaska Gold Rush

o Undersea Mining In a process called dredging, miners use large machines

similar to vacuum cleaners to collect sand and gravel from the sea floor

Used to extract salt deposits, phosphorite, diamonds, calcium carbonate, silica, copper, zinc, silver, and gold ore.

Expensive to access resources and extract

—Processing Minerals and Metalso After mining, ores and other extracted materials

are processed to separate the desired materials, combine them with other materials, or alter their properties.

oMinerals need to be separated from the ore to gain access to the desired metals

o Ore is crushed and ground into particleso Specific properties of minerals including density,

cleavage, magnetism, and conductivity are used to separate minerals from ore Froth flotation involves mixing finely ground ore with

water to form slurry which then has chemicals and air bubbles added to it, causing the desired mineral to float to the surface.

o Once separation is complete two products remain – the concentrated mineral and tailings (waste product).

oMost metal production techniques include smelting – heating ore beyond its melting point and combining it with other metals or chemicals. Alloys consist of metals that have been melted and

fused with other metals or nonmetal substances (ex: steel)

Lesson 3: Mining Impacts and Regulation

—Negative Impacts of Miningo Environmental impacts of mining include

increased erosion, increased sediment and debris, and pollution of water, land, and air. Mining can also have negative impacts on society.

oWhen people disturb a large area of land, erosion occurs faster than the soil can be replaced. Clearing land and removing soil and rock during strip

mining can lead to excessive erosion Placer mining disturbs stream banks and causes erosion Mountaintop removal leaves areas vulnerable to

flashfloods and mudslidesoWaterways can become clogged with excessive

amounts of sediment and debris which can block sunlight from reaching aquatic plants.

o Acid drainage occurs as the acid and the metals it leaches from rock seep into groundwater or enter streams and lakes as runoff. A natural process, but mining greatly accelerates it by

exposing more rock to the air at once Toxic to wildlife even at low concentrations Makes bodies of water unsuitable for drinking water or

recreational use

o Tailings contribute significantly to the water pollution because they are stored in impoundments (dams) at processing sites. Impoundments are designed to keep pollutants from

leaching out of the tailings and entering the soil and groundwater, but these systems sometimes fail.

o Open pit mining and mountaintop removal can cause air pollution as metal particles are released into the atmosphere. Miners receive the most exposure to this air pollution –

in subsurface mines miners inhale toxic fumes and coal dust which can lead to black lung disease.

o Some environmental scientists fear that excessive disruption of the sea floor will destroy habitats and organisms that have not been studied yet.

o Disruption of the sea floor may also cause metals to diffuse into the water and enter the food chain at toxic levels.

o Social impacts of mining include property damage, environmental damage, and conflicts. Mountaintop removal blasts can crack house foundations and

wells Floods and mudslides damage properties Loose rock tumbles into yards and homes Communities built on top of old subsurface mines are at risk

of sinkholes when those tunnels collapse Destructive to land and water resources In nations with weak or corrupt governments, violent conflicts

may arise over rights to lands that hold valuable minerals Trade in valuable minerals can also led to conflict

—Mining Regulationo Regulations that govern mining consider the

environmental and safety impacts of mining along with the economic costs to the industry

o General Mining Law of 1872 Partly in response to the California Gold Rush of 1849 Created some rules to manage mining activities Designed to promote mining Governs the mining of metallic minerals on public lands Changed to prohibit mining on certain types of public

lands

In early 2009, the Hardrock Mining and Reclamation Act was proposed which would end the patenting process and require miners to pay the government 4% of their profits for existing mines and 8% for new mines.• The money would be used for environmental cleanup and

community reimbursements• Not enacted

o The Mineral Leasing Act of 1920 governs the leasing of public lands for mining fossil fuels, phosphates, sodium, and sulfur.

o Surface Mining Control and Reclamation Act (1977) Coal mining companies are required to reclaim

(restore) the land after mining is complete in the area

Requires mining companies to post bonds to cover reclamation costs before their mining plans can be approved• Ensures that if a company fails to restore the land for any

reason, the government will have the money to do so Even on sites that are reclaimed, negative effects from

mining can be severe and persist for a long time. Restored sites do not generally replace the natural

biotic communities that were present before mining

oMining Safety The first law (1891) established ventilation

requirements for coal mines and prohibited hiring children under the age of twelve

The Federal Mine Safety and Health Act of 1977 regulates modern day mining safety

—Responsible Mineral Useo Because minerals are a nonrenewable resource, we

need to be concerned about finite supplies and ways to use them more responsibly, such as reusing and recycling.

o New technologies may make some minerals more in demand and others less in demand

o Advances in recycling help extends the lifetimes of some mineral resources

o Reusing and recycling decrease energy use and save consumers and businesses money Ex: extracting aluminum ore takes 20 times more energy than

obtaining it from recycled sources