10.1: Mineral Resources and Extraction

Resources

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. 

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 minerals resources are far below the surface of the earth. In these cases, subsurface mining must be used. Subsurface mining is the digging of tunnels or shaft 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

The room and pillar method is the most popular technique for subsurface mining.   This type of mining involves cutting networks of open areas (or rooms) into horizontal layers of coal.   Pillars of solid coal are created and left in place for structural stability.  

Another method of subsurface mining is called solution mining.     Also known as in-situ leach (ISL) mining, this technique can be used to extract mineral resources that are soluble in water.   In solution mining hot water is forced into mineral ore followed by compressed air.   The air causes the solution of hot water and dissolved mineral ores to rise to the surface.  

Surface mining

Surface mining is the mining of materials at the surface where miners are under the sky, not the ground, and includes

• Open-pit mining is the removal of material through an open hole in the surface, usually quite wide.
• Strip mining is the removal of surface materials to allow access to shallow materials underneath.
• Mountaintop removal is the literal removal of a mountaintop to expose materials - this is common in coal 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.   Approximately 90% of non-fuel mineral resources and 60% of coal is extracted in the United States using surface mining.   

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 remove the aluminum 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. The tailings are generally not useful and must be disposed of, which often presents environmental concerns. (Human environmental impacts are discussed in a later module.)

Impact on the Environment

  

The processes of extracting, refining, and using mineral resources can have a profoundly negative effect on the environment.   Surface mining permanently changes the land where it is being utilized.   This technique of mineral extraction disrupts and can even destroy ecosystems.   Subsurface mining has less impact on the environment and produces less waste, but it is also far more dangerous and expensive.   The physical impact of mining is not the only negative aspect of this form of mineral extraction.   Toxic chemical wastes produced in the process of mining and refinement can be carried to both surface and ground water supplies as well as emitted into the atmosphere.   The Surface Mining Control and Reclamation Act of 1977 was passed by the U.S. government in an attempt to lessen the environmental impact of mining.   This act requires mining companies to reclaim or restore most surface-mined land.  

Impact on Humans

Some resources must be extracted from underground mines. This process can be very dangerous for miners due to issues such as fires, explosions, and roof falls. According to the United States Department of Labor, 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.

On top of its toll on human lives, mining and burning coal can have many detrimental effects to the environment. Burning coal releases sulfur oxide into the atmosphere, which, you will learn, contributes to acid precipitation. In addition, burning this resource currently contributes to approximately one-third of the annual, global CO₂ emissions. This makes this mineral resource a major contributor to the enhanced greenhouse effect that is causing global climate change.

Primary Solutions

The 4 Rs:

• Reduction of resources (most effective)
• Repurposing of resources
• Reuse of resources
• Recycle of resources (least effective)

(Georgia Virtual School, CC BY-NC-SA)