10.1: Mineral Resources and Extraction
- Page ID
- 85641
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A resource is anything that can be useful, which covers quite a bit. In geology, we generally refer to things that can be commercially useful as resources, but not all resources are necessarily converted to money.
Resources can be classified as one of three types.
Three Types of Resources:
- Renewable: resources that can be remade, regrown, refreshed, or regenerated within a reasonable human timespan. The keyword in the definition is "can". Because a resources is renewable doesn't mean it will be renewed, just that given the right conditions it is possible. Examples of renewable resources are food products and the plants, animals, fungi, and protists they come from in addition to other products.
- Non-Renewable: resources that take a long time to form and also may only form under only special conditions - more than what is possible or practical for humans to wait for. Anything that cannot be renewed within a reasonable human timespan is considered non-renewable. Examples include all fossil fuels, minerals, and ore.
- Perpetual: gray area between renewable and non-renewable. Something that is in either infinite supply (for human purposes) like sunlight and wind, or which contains a supply that, even if it is technically non-renewable, it can be considered as such for humans, such as water.
Mineral Resources
Minerals are inorganic compounds and elements with a regular crystalline structure found in the earth's crust that can be used for a variety of purposes. Resources can often be obtained from minerals or mineral-like matter. This can be broken down into metallic and non-metallic mineral resources. In this definition, the word mineral is used loosely - things that do not technically meet the definition of a mineral can still be thought of as a mineral resource (as mineral-like matter, like volcanic glass).
Mineral resources can be organized into four main categories:
- Identified Resources: Identified as having a known location, quality, and quantity.
- Reserves: Resources that can be used in a cost-effective manner given the current prices of the specified resource.
- Undiscovered Reserves: Reserves of a given resource that are believed to exist.
- Other Resources: Mineral resources that have not yet been discovered or identified resources that are not considered to be reserves.
All minerals that are valuable to humans and, therefore, economically desirable for extraction are collectively called ore minerals.
Some common and important ores include:
|
Ore |
Metal/Use |
|---|---|
|
Argentite |
Silver |
|
Barite |
Barium |
|
Bauxite |
Aluminum |
|
Beryl |
Gemstones |
|
Bornite |
Copper |
|
Cassiterite |
Tin |
|
Chalcocite |
Copper |
|
Chromite |
Chromium |
|
Cinnabar |
Mercury |
|
Cobaltite |
Cobalt |
|
Galena |
Lead |
|
Gold |
Gold |
|
Hematite |
Iron |
|
Ilmenite |
Titanium |
|
Magnetite |
Iron |
|
Molybdenite |
Molybdenum |
|
Sphalerite |
Zinc |
|
Uraninite |
Uranium |
|
Wolframite |
Tungsten |
Non-Metallic Mineral Resources
Not all mineral resources are used to obtain metals. Some resources produce non-metallic items that can be used commercially. This includes many resources that become building materials.
|
Resource |
Use |
|---|---|
|
Rock Salt |
Food additive, aquarium supplies, snow/ice melt |
|
Sand |
Concrete, building materials, playgrounds, beach replenishment, glassmaking |
|
Clay |
Building materials, ceramics, art supply, pottery |
|
Gypsum |
Building materials (drywall) |
|
Limestone |
Road base, building materials, lime, cement |
Formation of Mineral Deposits
Minerals can be formed through a variety of processes. See Section 3.1 of this text for a review.
Extraction of Mineral Deposits
Ores are not useful, generally, by themselves. They must be mined - removed from their native surroundings using tools or machinery. Although in ancient times, mining was performed with simple tools, modern mining requires extensive amounts of heavy machinery. A location where mining occurs is a mine, although mines may be used to obtain resources other than ores or mineral resources (coal, for example, is mined).
There are several common types of modern mining:
Subsurface mining
Sometimes, mineral resources are far below the surface of the earth. In these cases, subsurface mining must be used, which causes less environmental damage but is more expensive and also more dangerous for miners due to fires, explosions, and cave-ins. In the early years of coal mining (1880-1910), there was an average of 1,500 deaths or more per year. 1907 was the deadliest year in U.S. coal mining history, with a total of 3,242 deaths. Over the years, conditions have thankfully improved, and the death toll of miners has decreased to an average of less than 35 people a year in the US, although it is much higher in many other parts of the world.
Subsurface mining is the digging of tunnels or shafts into the ground to obtain ores or other useful deposits and includes:
- Shaft mining - vertical shafts dug into the earth
- Drift mining - horizontal shafts dug into the earth
- Slope mining - diagonal shafts dug into the earth
- Room and pillar - cutting networks of open areas (rooms) into horizontal layers with pillars left for structural stability. The most popular method for subsurface mining.
- Solution/in-situ leach mining - hot water is forced into mineral ore, followed by compressed air, causing the solution of water and dissolved minerals to rise to the surface
Surface mining
In surface mining, extraction occurs when overburden (layers of rock and soil on top of a mineral resource) is removed and discarded as a waste product. Surface mining causes many extensive environmental problems, including air and soil pollution. Leachate, the contaminated water left over from surface mining, is of particular concern and leads to both surface and groundwater contamination.
The Surface Mining Control and Reclamation Act of 1977 was passed by the U.S. government in an attempt to lessen mining's environmental impact. This Act requires mining companies to reclaim or restore most surface-mined land. However, many mining companies have found loopholes to avoid following this law.
Approximately 90% of non-fuel mineral resources and 60% of coal are extracted in the United States using surface mining.
Techniques include:
- Open-pit mining - removal of material through an open hole in the surface, usually quite wide.
- Strip mining - removal of surface materials to allow access to shallow materials underneath.
- Mountaintop removal - literal removal of a mountaintop to expose materials, common in coal mining.
Mountaintop mining (MTM), while less hazardous to workers, has particularly detrimental effects on land resources. Companies use MTM to expose mineral and coal seams from the tops of mountains, destroying all vegetation and topsoil and disposing of the associated mining waste in adjacent valleys, which buries streams and other important habitats.
Processing
Mining alone is usually not enough to make use of most ores or other mineral resources. These ores and other resources generally must be processed before their final use. Bauxite, for example, contains aluminum, which may eventually be useful. However, bauxite is not pure, and even bauxite, which is closer to purity, must have the bauxite separated from other nearby minerals that may have been attached, then the aluminum must be removed from the bauxite.
Smelting is the process of melting a metal out of mineral ore.
Tailings are the remnants left over from the ore after the metals have been removed. They are not generally useful, and their disposal presents environmental and health concerns.
The Global Economics and Impacts of Mining
The economics of mining are such that, in many communities and parts of the world, entire economies are based on the extraction of minerals and fossil fuels, most of which are not meant to be used locally. The companies employing locals are most often multinational corporations working through a series of subsidiaries. There is also a modern-day land rush by companies and governments for minerals and fuels in areas of the world that have not yet been mined, such as in sub-Saharan Africa, parts of Asia, and South America.
In addition to the many environmental issues, this is difficult for the local populations, who do not have many alternatives for making an income. Once the seams are tapped out or the mines are no longer economically viable, the companies claim bankruptcy or vacate, leaving the local communities to try to diversify their economy once more and find a way to live with what is left of their environment.
Primary Solutions
The 5 Rs, in order of effectiveness:
- Refusing resources (most effective)
- Reducing resources
- Repurposing resources
- Reusing resources
- Recycling resources (least effective)
(Georgia Virtual School, CC BY-NC-SA)