Industrial nonmetals

Nonmetallic Earth resources consist of fertilizer minerals, raw materials for the chemical industry, abrasives, gemstones, and building materials for the construction industry. They provide the necessary base for a technological society.

Definition of Nonmetallic Resources

The definition of a nonmetal is problematic. To the chemist, a nonmetal is any element not having the character of a metal, including solid elements, such as carbon and sulfur, and gaseous elements, such as nitrogen and oxygen; this is the definition found in most dictionaries. To the economic geologist, however, a nonmetal is any solid material extracted from the earth that is neither a metal nor a source of energy. A nonmetal is valued because of the nonmetallic chemical elements that it contains, or because of some highly desirable physical or chemical characteristic.

Economic geologists consider the following to be major nonmetallic Earth resources: fertilizers, raw materials for the chemical industry, abrasives, gemstones, and building materials. A few minerals, such as asbestos and mica, are used for distinctive or unusual physical properties. As can readily be seen, with the exception of the gemstones, nonmetallic Earth resources lack the glamour of such metals as gold and platinum or such energy sources as oil and uranium. Nevertheless, nonmetallic Earth resources play an essential role in the world economy.

Except for gemstones, nonmetallic Earth resources have certain common characteristics. First, they tend to be more abundant in the earth’s crust than metals and are therefore lower in price. Nevertheless, most of them are needed in much larger quantities, so the total value of the substances produced is considerable. This is particularly true of the building materials needed for the construction industry. Second, nonmetallic Earth materials tend to be taken from local sources. Most of them are needed in such large quantities that transportation costs would be excessive if they were brought long distances. As a result, regional variations occur in the types of rock used for building stone and crushed rock. Third, problems of supply are not generally associated with nonmetallic Earth materials. Most of them are fairly abundant at the earth’s surface, and few major industrial nations are without deposits of each. None of these resources is classified as a strategic material by the United States. Finally, nonmetallic Earth materials tend to require very little processing before being sent to market. In fact, most of them are used in the raw state.

Fertilizers

The first category of major nonmetallic Earth resources is fertilizers. These substances are absolutely essential to a nation’s agriculture and food supply. The three most important elements for plant growth are nitrogen, potassium, and phosphorus. For years, nitrogen was obtained from nitrogen-rich Earth materials—either from the famous guano deposits in Peru, which were built up by accumulated bird droppings on coastal islands, or from the nitrate deposits in Chile, which cover the floor of a desert. In 1900, however, German chemist Fritz Haber discovered a way of manufacturing nitrates synthetically, using nitrogen extracted directly from the atmosphere. Today, the synthetic nitrate industry provides 99.8 percent of the world’s nitrogen needs.

The potassium required for fertilizers was originally obtained from wood ashes (hence the common name “potash”), and still is in many developing nations. In 1857, however, potassium-bearing salt beds were discovered in Germany. These had formed as a result of the evaporation of lakes in an arid climate, and they were the world’s major source of potassium until 1915, when Germany placed a wartime embargo on their shipment. This embargo forced other countries to explore for replacement deposits, and similar salt beds were eventually found in the former Soviet Union, Canada, and the western United States.

The third element required for fertilizers, phosphorus, was originally obtained from guano or from bones. These sources have been replaced by natural phosphate rock deposits, which are widely distributed around the world. Most of these deposits occur in marine sedimentary rocks, and it is believed that deposition of the phosphate resulted when cool, phosphorus-bearing waters upwelled from the sea floor and were carried into shallow environments, where the phosphorus was precipitated. The largest US phosphate deposits are found in Florida and North Carolina.

Raw Materials for Chemical Industry

The second major category of nonmetallic Earth resources consists of raw materials for the chemical industry. In terms of total production, the most important of these is salt, for which the mineral name is halite. In addition to its use as a dietary ingredient, salt is the raw material from which a number of important chemicals are made, including chlorine gas, hydrochloric acid, and lye. In colder climates, salt is also used for snow and ice control on roads. Salt is produced by the evaporation of seawater and by the mining of underground salt deposits. Although underground salt commonly occurs as deeply buried layers, nature has an interesting way of bringing the salt to the surface. Since salt is lighter in weight than the overlying rocks and is capable of plastic flow, it rises through the surrounding rocks as a salt plug with a circular cross-section, known as a salt dome. Salt domes are particularly common along the Louisiana and Texas Gulf Coast and are even more important as petroleum traps than as sources of salt.

Another important raw material for the chemical industry is sulfur, a soft yellow substance that burns with a blue flame. The major industrial use for sulfur is in the production of sulfuric acid. Large quantities of sulfuric acid are used in converting phosphate rock to fertilizer. Sulfur also has important uses in the manufacture of insecticides. Most of the sulfur used in the United States comes from the salt domes of the Louisana and Texas coast, where it is found in the upper part of the dome. Superheated steam is pumped down through drill holes to melt the sulfur, then the liquid sulfur is brought to the surface by the pressure of compressed air. In recent years, the removal of sulfuric acid from smokestack emissions has sharply reduced the demand for sulfur extracted from salt domes. Additional raw materials for the chemical industry include several that are obtained from the beds of dry desert lakes: sodium carbonate and sodium sulfate, which are used in the manufacture of glass, soaps, dyes, and paper, and borax, which is used in making detergents, certain types of glass, and explosives. Another product is sodium bicarbonate, the familiar baking soda.

Abrasives

The third major category of nonmetallic Earth resources is abrasives, which are materials used for grinding, cleaning, polishing, and removing solid material from other substances. Most abrasives are very hard, but those used for cleaning porcelain sinks and silverware need to be fairly soft, so as not to scratch. Abrasives can be either natural or human-made. The natural abrasives are rock and mineral substances that have been extracted from the earth and are then either used in the raw state, such as a block of pumice, or pulverized and bonded into sandpapers, wheels, saws, drill bits, and the like. Artificially made abrasives, however, are gradually coming to dominate the market.

The most common abrasive is diamond, which has a hardness of 10 on a scale of 1 to 10 and is the hardest known natural substance. Most natural diamonds are unsuitable for use as gems, however, so about 80 percent of them are used as abrasives. In 1955, General Electric developed a process to make industrial diamonds synthetically, and by 1986 two-thirds of the world’s industrial diamonds were produced synthetically. Other important natural abrasives include the following: corundum, the second hardest natural substance, with a hardness of 9; emery, a gray-to-black mixture of corundum and the iron mineral known as magnetite; and garnet, a reddish-brown mineral with a hardness of approximately 7, which is commonly used in sandpaper. Ninety-five percent of the world’s garnet comes from the Adirondack Mountains in New York State.

Unusual Physical Properties

Among minerals used for their unusual physical properties are barite and barium sulfate, which is unusually dense for a nonmetallic mineral. It has some medical uses because it absorbs X rays, but its principal use is in the petroleum industry, drilling mud. Powdered barite is mixed with water and poured down oil wells as a coolant and lubricant. Its density helps keep oil and gas from escaping to the surface. Mica, which splits into thin, transparent sheets, is used in electrical applications because of its resistance to breaking and melting. Asbestos is obtained from flame-resistant mineral fibers that can be woven into fireproof cloth or mixed with other substances to make fireproof roofing shingles and floor tiles. Concerns about the health hazards of asbestos use arose in the 1970’s. Fine particles of asbestos dust can lodge in the lungs, causing asbestosis and lung cancer. As a result, the US consumption of asbestos has declined markedly since the 1970s.

Gemstones

The fourth major category of nonmetallic Earth resources is gemstones. These are used primarily for adornment and decoration. Unlike the other nonmetals, gems are generally not abundant, have a moderate to high value, come in only small quantities, are rarely of local origin, and are often in only short supply. Desirable properties in a gem are color, brilliance, transparency, hardness, and rarity. Gems are categorized into two principal groups. Precious gems are diamond, ruby, sapphire, emerald, and pearl. All of these can be produced synthetically, except for high-quality gem diamonds. Ruby and sapphire are varieties of corundum and may exhibit “stars.” Emerald is a variety of beryl with a hardness of 8. Pearls have a hardness of 3 and are technically not true minerals, even though they consist of calcium carbonate, because they are produced by a living organism. Semiprecious gems include some one hundred different substances. Most are minerals, except for amber (hardened resin from a pine tree), jet (a dense variety of coal), and black coral (a substance produced by a living organism). As attractive and valuable as gems are, the abrasives diamond and corundum are vastly more valuable to technology than they are as gemstones.

Building Materials

The fifth major category of nonmetallic Earth resources is building materials for the construction industry. They include building stones obtained from quarries, such as granite, sandstone, limestone, marble, and slate. There is also a high demand for crushed rock, which is used in highway roadbeds and for concrete aggregate. Sand and gravel also are used in making concrete. In some parts of the country, construction materials are becoming scarce not because of rarity but because of political opposition to the extraction of resources from residential areas. In addition, many useful products are prepared from Earth materials, such as cement, which is made from a mixture of limestone and clay; plaster, which comes from the mineral gypsum; brick and ceramics, which use clay as their raw material; and glass, which is made from very pure sand or sandstone rock.

Assuring Supplies of Nonmetallic Resources

An important way in which nonmetallic Earth resources are studied is to analyze proven reserves. Proven reserves are supplies of a mineral substance that remain in the ground and are available for future removal. When experts compare the present rates of production of various nonmetallic Earth resources with the same resources’ proven reserves, they can predict which resources may be in short supply someday. In the case of the phosphate rock used in making fertilizers, for example, analysts have found that the United States’ phosphate reserves will begin to decline by about the year 2010.

Economic geologists also study ways to assure that adequate supplies of nonmetallic Earth resources will be available for future needs. In the case of phosphate, for example, the need for such studies is critical. Such a program of exploration for new phosphate supplies, or for any other nonmetallic resource, must begin with a full understanding of the ways in which the mineral resource originates. Only when geologists understand the conditions under which valuable concentrations of mineral substances form can they successfully search for them.

In the case of phosphate, careful scientific study has shown that the cold waters found in the deep ocean contain thirty times as much dissolved phosphorus as do warm shallow waters. This observation suggests that when cold, deep waters are brought to the surface and warmed (by upwelling from the ocean floor, flowing into coastal zones across shallow submarine banks) the warming effect makes the phosphorus less soluble, and it precipitates. As a result, scientists are exploring for phosphates along present or former continental margins, where such upwelling might have taken place.

Another way in which adequate future supplies of nonmetallic Earth resources can be assured is by creating nonmetals synthetically in the laboratory. A good example of this process was the successful synthesis of industrial diamonds by General Electric in 1955. Before then, the United States had no industrial diamond production or reserves and was totally dependent on supplies purchased in the world market, then controlled by the De Beers group in South Africa. General Electric was able to create diamonds synthetically by subjecting the mineral graphite—which, like natural diamond, is composed of pure carbon—to incredibly high temperatures and pressures in a special sealed vessel, using molten nickel as a catalyst. By 1986, two-thirds of the world’s industrial diamonds were being produced by this process, and the De Beers monopoly on industrial diamond production was broken.

Continued Importance

The United States is fortunate in having a plentiful food supply, and most Americans rarely think about the importance of fertilizers. They are essential, however, for successful agricultural operations. Plant growth requires ample mineral matter, partly decomposed organic matter (humus), water, air, and sunlight. Of these, mineral matter is crucial, because it provides the nitrates and phosphates essential for healthy plant growth. These substances are quickly used or washed away, and they must be replenished regularly so that the soil does not become worn out and infertile. Worn-out soils are encountered frequently in developing nations, where farmers are often too poor to buy fertilizers.

Industrial chemicals such as salt, sulfur, and borax appear on grocery shelves in their pure state, but they are also present as ingredients in products where one would never suspect their existence. In addition, they are frequently needed to manufacture everyday products, such as drinking glasses or writing paper. Salt is a good example. In addition to its use as table salt, it is an ingredient in almost every prepared food item on the grocery shelf. Abrasives, too, are common on grocery shelves, although the word “abrasive” may not be written on the package. They are in toothpaste, silver polish, bathroom cleanser, pumice stones, sandpaper, and emery boards.

Nonmetals are used in many common construction materials. The beautiful white buildings in Washington, DC, are made of pure white Vermont marble. Granite, however, is preferred for tombstones, because it resists weathering more successfully. It is used also for curbstones in northern cities, because it holds up best under the repeated impacts from snowplow blades. The days of buildings faced with cut stone, however, are on the wane; production and transportation costs are simply too high. Today’s private dwelling is more likely to be built of cinder blocks manufactured at a plant outside the city, and downtown office towers are sheathed with walls of glass and prefabricated concrete, all of which ultimately depend on nonmetallic mineral resources.

Principal Terms

asbestosis: deterioration of the lungs caused by the inhalation of very fine particles of asbestos dust

catalyst: a chemical substance that speeds up a chemical reaction without being permanently affected by that reaction

guano: fossilized bird excrement, found in great abundance on some coasts or islands

metal: a shiny element or alloy that conducts heat and electricity; metals are both malleable and ductile

proven reserve: a reserve supply of a valuable mineral substance that can be exploited at a future time

sedimentary rock: rock formed from the accumulation of fragments weathered from preexisting rocks or by the precipitation of dissolved materials in water

star sapphire/ruby: a gem that has a starlike effect when viewed in reflected light because of the mineral’s fibrous structure

strategic resource: an Earth resource, such as manganese or oil, which would be essential to a nation’s defense in wartime

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