Nonrenewable Resources: Minerals

 
 A nonrenewable resource is a natural resource that is present in limited supplies and depleted by use. It's basically a limited resource that we are extracting from the ground faster than it can replenish itself. (9) Examples of nonrenewable resources are copper, gold, silver, zinc, aluminum, coal, oil and natural gas. For my speech, I will concentrate on mineral resources.

 

Mineral resources are one of the major kinds of nonrenewable resources. Mineral resources are not uniform throughout the earth. The geological processes that formed these mineral resources occurred many millions of years ago. The distributions of these mineral resources are unevenly throughout the earth. Currently we are exploiting our mineral resources at a high rate. As we continue to use our mineral resources, they will be harder to find and more costly to develop. (8)

 

I will be focusing primarily on three mineral resources:

Copper

Gold

Silver

 

The Formation of Minerals

One type of formation is a natural process called magmatic concentration. As molten rock from a volcano cools, it becomes solid deep in the earth's crust. The molten rock often separates into layers with the heavier iron, magnesium part of the rock settling on the bottom and the lighter silicate rock settling on the top. Varying concentrations of the minerals (depending on the cooling rate) are found in the rock layers. The variations create different element combinations. One solid element variation is copper. (8,9)

Another type of formation is the hydrothermal process. This process involves heated groundwater. As water seeps through cracks and dissolves certain minerals that were formed from magmatic concentration, the water encounters sulfur (a common earth element). A chemical reaction occurs and creates a metal sulfide. Metal sulfides are not soluble in water and therefore they settle as solid deposits. Some of the solid deposits are responsible for the creation of some copper, as well as silver, gold, lead, and zinc. (8,9)

Sedimentation is also a process that forms mineral deposits. Sedimentation is the weathering and breaking off of mineral particles that have been already formed by magmatic concentration or the hydrothermal process. These broken off particles can be deposited along riverbanks, deltas and sea floors. This explains why we can find certain minerals in these places. (8,9)

Steps in discovering and mining mineral deposits

There are three main steps to make mineral deposits available for human consumption.

Locate the Mineral

Extract the Mineral

Process the Mineral

Locating mineral deposits is really by luck. There is no set way to find a deposit. Most mineral deposits are found by stumbling upon them while drilling and exploring for other materials or using geological maps.

Mineral extraction is done by several different techniques depending on how accessible the mineral.

One method is surface mining. This is when the resource is near the surface and is extracted by first removing the solid subsoil and overlying rock. There are two types of surface mining. (7)

One is open pit mining. Open pits are made by drilling a giant hole in the earth. This large hole is referred to as a quarry. Many of the largest open pit mines, such as those in the southwest United States are from copper extraction. (7)

The world's largest open pit mine is at Bingham, Utah.

 

Bingham Canyon Copper Mine is two and a half miles wide and half a mile deep. It is one of the most efficient copper producing mines in the world. The Bingham Canyon Mine has produced over 14 million tons of copper, more than any other mine on the earth. http://www.mining-technology.com/projects/bingham/index.html

Another type of surface mining is strip mining. This is where a trench is dug to extract the mineral. The mining method involves removal of the rock to expose the minerals. The removed rocks are usually scooped up and dumped to the rear of the trench. The mining then continues along a strip that extends far. Then another trench is dug parallel to the first trench and the waste rock from the second trench is dumped into the first trench. (7)

There are also underground mining techniques used in mineral extraction. This is known as subsurface mining. Subsurface mining involves shaft mines and slope mines. Shaft mines are directly vertical in the ground. The ore is broken apart underground and hoisted through the shaft to the surface in buckets. Slope mines are slanting passages that make it possible to haul broken ore out of the mine in cars. (8,9,11)

Processing minerals

Processing minerals often involves a smelting process. This is the melting of the ore at high temperatures to help separate impurities from molten metal. Smelting takes place in a large furnace. The ore, limestone and coke (modified coal used a fuel) are added at the top of the furnace, while heated air or oxygen is added at the bottom. The iron reacts with the coal to form molten iron and co2. The limestone reacts with the impurities in the ore to form slag. Slag is deposited at one end and iron is deposited at the other. There is an exhaust on the furnace for the gases that are emitted. (8,9,11)

 

Mining and the Environment

All of the mining and processing methods explain have environmental impacts. Mining disturbs and damages the land, and processing and disposal of minerals pollute the air, soil and water.

The process of strip mining involves stripping of the vegetation, soil and rock layers to remove the minerals. Then you must dispose of the waste rock or fill that has been stripped. The fill is usually replaced in long ridges called spoil banks, because this is the easiest way to dump it cheaply and quickly. Spoil banks are very susceptible to erosion and weathering. Rainfall picks up numerous chemicals (such as acid from the common earth element sulfur) from the newly exposed earth. The sediment/rain runoff runs into streams causing pollution from the toxic compounds that were picked up. The toxic compounds affect numerous kinds of aquatic life and groundwater can also be contaminated. Acid runoff has contaminated 6700 streams in the US. Steep spoil banks are very slow to revegatate. They do not have natural topsoil, or soil development and the establishment of natural biological communities occur slowly. The 1977 federal Strip Mining Control Act requires better restoration of strip-mined lands but it's very difficult and expensive. Even if soil is carefully replaced, it will take centuries to regain its former fertility by natural processes. (8,9,4)

All mining involves the separation of mineral from the surrounding rock. The surrounding rock must then be disposed of in some way. These pieces of rock ore are usually piled on the surface of the earth where they are known as mine tailings. It's difficult to get vegetation to grow on these deposits. Also some tailings contain materials such as asbestos, arsenic, lead and radioactive materials. These are harmful to humans and other forms of life.

Smelting plants have the potential to emit large amounts of air pollutants during mineral processing. One is sulfur. Sulfur creates sulfuric acid when it reaches the atmosphere. This contributes to acid rain. Acid rain is rain that is more acidic than normal. Acid rain's spread and damage involves disturbing the soil, water, and the life cycles of plants and animals. (8,9,4)

http://www.epa.gov/docs/acidrain/student/aciddef.html

 

Another example of a smelting pollutant is a result of zinc smelting. Cadmium (used in dry cell batteries) is found in zinc and emissions from zinc smelters create cadmium contamination. In humans cadmium is linked to high blood pressure, diseases of the liver, kidneys and heart and certain types of cancer. (11)

http://www.osha-slc.gov/SLTC/cadmium/index.html

 

The Bunker Hill Superfund Site is a former mining and smelting complex located in Kellogg, Idaho. The site was contaminated by years of mining and smelting. It began in the 1800's. The mines and smelters produced lead, zinc, cadmium, silver, and gold. Lead, arsenic, cadmium and zinc are the primary contaminants at Bunker Hill. At Bunker Hill there are mine tailings, past air emissions, acid mine drainage and inflow of contaminants from other upstream mines operations. A fire at the smelter in 1973 damaged air emission controls and high lead emissions were released in the air. A study found that 98% of 1 to 9 year old children living within one mile of the smelter had blood lead levels in excess of 40 g/d.

The effects of the contaminants at Bunker Hill are small children and pregnant women could suffer neurological effect from the lead. Childhood lead toxicity may have permanent effect including decreased intelligence, impaired hearing and reduced growth. Zinc exposure can cause stomach and digestive problems. It may also interfere with the immune system.

http://www.nws.usace.army.mil/geotech/bunker/bunker.htm

 

Many developed countries have regulations to reduce environmental damage from mineral consumption. Some of the policies are to prevent pollution, restore mining sites and exclude wilderness sites from mineral development.

 

Longtime Future for Scarce Minerals

Minerals are our most valued resource. They are being mined at a rate in which they can't recover. Mineral reserves (deposits that are profitable to extract) of gold, copper, silver, etc. are slowly depleating away. Example: Based on the rate of consumption in 1994, copper reserves will only last until 2029. (11) So what can we do to ensure that in the future we will still have minerals?

It is possible that new deposits can be found. Advanced mining technology may make it possible to profitable extract minerals from mineral resources of low grade ore or find new deposits in unexplored territory. However, there are the consequences of hurting the environment. The best way to approach this problem is through mineral conservation.

 

Mineral conservation

Topic of discussion…

  1. Mineral Substitution: Using more abundant materials in place of scarce minerals.
  2. Recycling: Don't throw away aluminum cans.
  3. Reuse: Rinse out your beverage containers.
  4. Changing mineral requirements: Become a low waste society.

 

 

Bibliography
 

1. Bunker Hill Supefund Site (1999, April 16). Bunker Hill Superfund Site. <http://www.new.usace.army.mil/geotech/bunker/bunker.html>

2. Hoffman-Thome Lila (1995-1999). Cultivating Our Non Renewable Resources. <http://www.pookas.com/cols/col.1-06-96A.shtml

3. Haugland, Erick; Merk, Andrew; Twedt, Kevin. Non Renewable Resources. <http://tqd.advanced.org/2763/Electricity/Generating/Nonrenewable.html

4. Environmental Protection Agency. What is Acid Rain? <http://www.epa.gov/docs/acidrain/student/aciddef.html

5. The Website For The Mining Industry (1999, July 21). Bingham Canyon. <http://www.mining-technology.com/projects/bingham/index.html>

6. Craig, J., Vaugh D., Skinner B. 1988. Earth's Resources. New Jersey, Prentice-Hall, Inc.

7. Kesler, S. 1994. Mineral and Economic Resources. New York, Macmillan College Publishing Company.

8. Enger, E., Smith, B. 1999. Environmental Science, A Study Of Interrelationships. McGraw-Hill Publishing Company.

9. Berg, L.; Johnson G.; Raven, P. 1998. Environment 2nd Edition. Chapter 15, pgs. 328-347.

10. Newell, R. Mining. Geotimes. September 1997.

11. Cunningham, Saigo. 1997. Environmental Science, A Global Concern. McGraw-Hill Publishing Company.