Chapter 13: Mineral Resources and Mining

Lesson 1: Minerals and Rocks

What are Minerals? A mineral is a naturally occurring, inorganic solid that has an orderly crystalline structure and a definite chemical composition. To be a mineral, a substance must be formed by processes within Earth, on the surface of Earth, or within organisms.

Most minerals are compounds made of two or more elements Inorganic materials do not contain carbon-carbon and carbon-hydrogen bonds 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 Most minerals are compounds made of two or more elements

Mineral Formation Minerals 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. Magma is a molten mixture of substances that forms deep within Earth When magma emerges at Earth’s surface it is called lava

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

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

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

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

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

Metamorphic 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? Mining companies seek and gather valuable resources such as metals, nonmetallic minerals, and fuel sources. Mining involves breaking into the ground to gain access to minerals, fossil fuels, or water, and extracting them. 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

Nonmetallic minerals may actually contain metal as a chemical component, but they are not mined for the metal. One of the most commonly mined fuels is coal. Other fuels, such as petroleum, natural gas, oil sands, and methane hydrates, as well as groundwater are also extracted from Earth.

Mining Methods Mining companies have developed many techniques to access resources close to the surface of Earth, deep underground, and even underwater.

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.

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.

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.

Mountaintop 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.

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

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

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 Metals After mining, ores and other extracted materials are processed to separate the desired materials, combine them with other materials, or alter their properties. Minerals need to be separated from the ore to gain access to the desired metals

Ore is crushed and ground into particles 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.

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

When 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 mudslides Waterways can become clogged with excessive amounts of sediment and debris which can block sunlight from reaching aquatic plants.

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

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.

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.

Some environmental scientists fear that excessive disruption of the sea floor will destroy habitats and organisms that have not been studied yet. Disruption of the sea floor may also cause metals to diffuse into the water and enter the food chain at toxic levels.

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 Regulation Regulations that govern mining consider the environmental and safety impacts of mining along with the economic costs to the industry

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

Surface Mining Control and Reclamation Act (1977) The Mineral Leasing Act of 1920 governs the leasing of public lands for mining fossil fuels, phosphates, sodium, and sulfur. 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

Mining 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 Use 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. New technologies may make some minerals more in demand and others less in demand Advances in recycling help extends the lifetimes of some mineral resources 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