What is meant by the term "mineral resources?" Mineral resources is the name given to minerals as well as fossil fuels, like oil, natural gas, and coal.
What are fossil fuels?
The three most common fossil fuels are coal, oil, and natural gas. They are derived from once living organisms, and they can be processed to yield energy. Strictly speaking, none of these substances are true minerals. Coal lacks the crystal structure of minerals and is chemically heterogeneous; true oil is a liquid, and natural gas is gaseous.
Coal is made from plant remains and is used in the production of electricity and chemicals as well as in the steel-making process. Beginning about 300 million years ago, extensive swampy forests covered the low-lying flat margins of continents and shallow inland seas. Over millions of years, plants grew and died falling into the swamp. From time to time, the swamps were covered by sands and mud, preventing the complete decomposition of the plants. Eventually the great weight of sediments compacted the plant material, forming peat and natural gas. More pressure and heat caused chemical changes that converted peat to coal. Coal is classified into four main kinds depending on the proportions of carbon, oxygen, and hydrogen it contains. The four kinds are anthracite, bituminous, subbituminous, and lignite. Anthracite has the greatest heat content and lignite the least. In the U. S. over 56 percent of the electricity is produced from coal, and the proportion is likely to increase in the future. Although coal reserves exist in thirty-two of our fifty states, the largest deposits are in Illinois, Iowa, Utah, Wyoming, and the Appalachian states.
Oil is formed from the remains of free-floating planktonic organisms which live in the open ocean. As sediment, rich in these organisms, is buried and compacted, the organic matter is altered. Near the surface, bacteria turn some of the organic matter to methane (natural gas). Deeper burial temperatures of 50° to 150°C promote the formation of oil. Above 150°C, oil is inorganically converted to methane. Oil and natural gas migrate from the site of formation through porous rocks (reservoir rocks). Oil and gas will accumulate in the reservoir rocks if an impermeable seal caps the porous rock. Oil as old as 580 million years has been recovered, but most is younger than 200 million years. Most natural gas is younger than 300 million years. The largest regions where oil has been found are in Russia, Saudi Arabia, North Africa, the North Sea, the north slope of Alaska, and the U.S. Gulf Coast. Oil is used primarily to produce diesel fuel and gasoline for transportation and as a new material for plastics and chemicals. Natural gas is used to make electricity and heat homes. Worldwide, the reserves of oil and natural gas are equal to each other, but are much less than those of coal. At the present time, oil and gas are being consumed more rapidly than they are being discovered. We live in an era when oil and gas are our principal sources of energy. Oil and gas are nonrenewable resources; and it is anticipated that sometime in the early to middle part of the next century, world oil and gas production will decline, forcing society to use alternative sources of energy.
What is geothermal energy?
Abnormally hot rocks can be found near the earth's surface. Groundwater, coming in contact with these rocks is heated and emerges as hot springs or geysers. These regions of hot water are called geothermal fields. Three types of fields are known: Warm waters less than 85°C, dry-steam (mostly steam), and wet-steam (mostly water). Warm-water systems are used mainly for space heating and greenhouses because the amount of heat is not sufficient to generate electricity. In dry-steam systems, such as at Larderello in Italy, water boils underground making steam that is tapped directly by wells. The steam powers turbines that make electricity. At the Salton Sea in Southern California, wet-steam is used to generate electricity. In wet-steam systems, very hot water is brought to the surface; there it turns instantly (flashes) to steam, and the steam is used to power turbines and produce electricity. The hot water in wet-steam carries abundant, dissolved metals and minerals. Efforts are now being made to recover some of the metals and other minerals, producing fresh water as a by-product. |
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Geothermal energy makes up a very small portion of the energy we use and is only important in regions where hot water occurs near population centers.
What is the importance of mineral resources?
It has been said that if a substance cannot be grown, such as wood, then it must be extracted from the earth. This is literally true, for even new materials made in the laboratory must be made from elements originally present in the earth either in the form of minerals or organic substances (coal, oil). Ironically, many things that are grown would not grow without the aid of mineral resources used in fertilizers or agricultural tools. Some mineral resources are used in the form in which they are mined, but other mineral resources are treated to separate a specific element, usually a metal, that is then used to make a product. For example, halite (sodium chloride, NaCI) is used directly as table salt; whereas, silver metal is extracted from acanthite (silver sulfide, Ag2S) and then used in photographic film.
Food, water, buildings, highways, automobiles, electrical appliances, electronic devices, chemicals, and even medicines all contain mineral resources (or elements derived from them), or mineral resources have been involved in making or using them. Consider the hamburger, and think about the bun. The hamburger bun is the product of a modern society that is highly dependent on minerals. Wheat used in making the bun is planted by a farmer using a tractor which runs on gasoline that is refined from petroleum which is usually pumped from great depths in the earth and is refined with the aid of metal catalysts (germanium), and the tractor itself is made of many metal parts (iron, aluminum, zinc, lead, copper, silicon). The wheat seedlings are irrigated by water carried in copper or iron pipes and is fertilized with mixtures made from phosphorous, nitrogen and potassium. After harvesting with a combine, also made of metal parts, wheat is mechanically ground in a metallic or ceramic grinder. Baking takes place in an electric oven. Of course, electricity is generated by turbines made of stainless steel (iron + chromium) and is delivered through copper wires. Finally, the bun is transported by truck over highways made with iron and concrete (calcite, dolomite and clay) to a store made from metal parts, concrete, brick (clay), and glass (quartz). The beef is transported in refrigerated containers by truck or train to the store. At the electronic cash register, the customer pays for the hamburger with money made of metals (bills and credit cards contain metals). Returning home from the store by bicycle, bus, or car, the customer relaxes to savor the hamburger and watch television on a color set made with thirty-five different metals. Catalytic converters, made of platinum in the car exhaust system, cut down on atmospheric pollution caused by the use of gasoline. Cleaning up after the meal may require soaps or detergents which contain minerals. Finally, if the hamburger gives you heartburn, that too can be relieved by antacids which contain the minerals calcite and talc. It is impossible to imagine a daily activity in our society which does not involve the use of minerals directly or indirectly.
Large amounts of mineral resources are mined annually. Approximately eight tons of new mineral resource materials required for each U.S. citizen include: 805 kg (1775 lbs.) of iron, 23 kg (51 lbs.) of aluminum, 9 kg (20 lbs.) of copper, 5 kg (11 lbs.) of lead, 4 kg (9 lbs.) of zinc, 160 kg (353 lbs.) of clays, 165 kg (364 lbs.) of salt, 165 kg (364 lbs.) of phosphate, and 6695 kg (14,762 lbs.) of building materials (minerals found in stone, sand and gravel, and cement).
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