Minerals for Making Things

            Throughout history, people have made use of materials from the earth to make their life easier. Tools made of flint, bronze, copper, and iron have been found in homes of ancient people. The materials for these tools were made of minerals from the earth. Generally, minerals can be thought of as the solid, nonliving, natural materials found in the earth. The earth's supply of minerals was formed over millions of years. Minerals are a nonrenewable resource.
            Many minerals have a name that ends in ite. For example, the mineral that salt comes from is called halite. Iron comes from the minerals hematite and magnetite.
            Many resources, such as air and soil, are readily available for use. But minerals must first be mined, or taken from the earth. Minerals that are mined are often called ores. Some ores, such as copper ore and iron ore, are often found at or near the surface. They can be mined by a surface method such as open-pit mining. Other minerals, such as silver and lead ore, are often found deep inside the earth. They must be mined by a method such as shaft mining.
            Most minerals must also be refined before they can be used. That is, impurities such as waste rock in the ore must be removed. For example, copper ore is crushed and screened. Chemicals are added to help remove some of the impurities. Then it is heated, and more chemicals are added until the desired purity is reached.
            After some minerals are refined, they are combined with other minerals. A combination of two or more minerals, usually metals, is called an alloy. For example, after iron ore is refined, metallic minerals such as chromium or nickel might be added to form an alloy of steel.

Common Uses of Some Minerals

Aluminum. Door and window frames, screens, food containers, foil food wrap, kitchenware, alloys (for strong and lightweight metals), toothpaste tubes, appliances, insulation.
Quartz. Glass, gemstones, radio and TV parts.
Gold. Jewelry, dental fillings, standard for money.
Asbestos. Safety clothing (such as firefighters' suits, gloves, and helmets), fireproof curtains and awnings, insulation, roofing shingles, wallboard, tiling.
Lead. Solder, plumbing, car batteries, radiation shielding, printers' type, pewter eating utensils and other objects, glass, ceramics, insecticides, medicines.
Mercury. Thermometers, silent electric switches, batteries (for small radios, cameras, and hearing aids).
Plaster of Paris. Plaster for walls and casts, cement, wallboard, soil conditioner, paint, filters, insulation.
Copper. Electric wiring, jewelry and other ornaments, alloys (for brass and bronze hardware), plumbing, coins.

Iron

            Iron is our most useful metal. It has many uses. It is used in shipbuilding; in the manufacture of locomotives, automobiles, pipelines, generators, containers, nails, bolts, and countless other things. However, iron is not found free in nature. It is combined with one or more other chemical elements. The product taken from the earth is called iron ore.
            Iron is extracted from iron ore in large blast furnaces. Iron ore is mixed with coke and limestone; then it is put into a blast furnace and heated. This treatment separates the iron from the iron ore. Melted iron flows out at the bottom of the furnace in a white-hot stream. The molten iron from the blast furnace is called pig iron. It contains some impurities which make it too brittle for many uses. Most of it is placed in an open-hearth furnace where it is converted into steel.
            Steel consists chiefly of iron, a small amount of one or more other metals, and some carbon. Stainless steel contains about 12% of chromium and some nickel. It is used to make high-grade cutlery. It is not affected by acid, and it will not rust.
            Manganese is used as a hardening ingredient in most steels. The metal tungsten is also present in some steels. Tungsten steel is used in making machine tools that must retain a sharp edge at the high temperatures caused by friction. More than 30 different kinds of steel go in the making of an automobile.

Aluminum

            Aluminum is a very useful metal. It is a light, strong metal. It is also an excellent conductor of heat and electricity. It is resistant to air, water and acids. Many pots and pans are made of aluminum.
            Aluminum is usually mixed with small amounts of other metals which make it harder and stronger. These mixtures are called aluminum alloys. Aluminum alloys are used to build airplanes, railroad cars, buses, ladders, chairs, lawnmowers and many other articles.
            Aluminum is very plentiful, but it is not found free in nature. It occurs in clay as alumina, an oxide of aluminum. One shovelful of the right kind of clay aluminum, today, is extracted from the ore called bauxite. The richest deposits of bauxite in the United States are found in Arkansas.

Copper

            Copper has been known since ancient times. It is sometimes found free in nature, but most of our copper, today, is extracted from copper ores. Copper is a good conductor of electricity, and this is its most important use. More than 30 million homes in the U.S. are wired with copper wire. Copper is also a good conductor of heat. Therefore, large amounts are used for making kettles and boilers. Large quantities of copper are also used in the manufacture of automobiles and locomotives.

Mercury

            Mercury is the only metal that is a liquid at normal temperatures. It flows through glass tubes without wetting the surface. And it contracts and expands regularly with changing temperatures. These qualities make it a suitable liquid for use in thermometers. Mercury makes alloys with most metals very easily. Mercury alloys are called amalgams. Your dentist makes amalgams of silver or gold for filling teeth. The main source of mercury is a red mineral called cinnabar. Cinnabar is a compound of mercury and sulfur. When this mineral is heated, the mercury is set free as mercury vapor. The mercury vapor is recaptured in cool chambers where it condenses as liquid mercury.

Other Useful Metals

            Zinc. Zinc is a widely used metal. It is used to galvanize iron. Galvanized iron is iron coated with molten zinc. A thin coat of zinc over iron prevents the iron from rusting. Zinc is also one of the ingredients in some paints and skin ointments. Much zinc is used in making certain alloys.
            Brass is an alloy of copper and zinc.
            German silver contains zinc, copper, and nickel.
            Bronze contains zinc, copper, and tin.
            Gold and silver are precious metals. They are attractive in color and have a beautiful luster. However, they are soft metals. They are usually alloyed with copper or some other metal to increase their hardness for use in coins, jewelry, and ornaments. The purity of gold is measured in carats. Twenty-four-carat gold is pure gold; 18-carat gold is 18/24 pure gold and 6/24 other metal; 16-carat gold is 16/24 pure gold and 8/24 other metal; and so on. Because gold and silver are expensive metals, many articles of fine jewelry and tableware are not made of solid gold or solid silver; they are simply coated with gold or silver. Such articles are said to be "gold-plated" or "silver-plated."

New Metals

            Metals are not evenly distributed in the earth's crust, and all countries are short of some of them. Once metals are taken from the earth, there is no second crop. They cannot be renewed.
            It is possible to make much greater use of aluminum and magnesium, both of which are abundant in the earth's crust. Then again sea water is an enormous reservoir of magnesium and other metals. But metals are so thinly scattered in sea water that it is expensive to recover them. For example, 800 tons of sea water must be processed to obtain 1 ton of magnesium. The most promising future supply is to develop "new" metals such as vanadium, beryllium, titanium, and zirconium.
            Titanium is a most promising new metal. It is lighter than steel and, when alloyed with iron, chromium, and molybdenum, it is quite as strong as stainless steel and even more resistant to corrosion. Titanium is clearly a constructional material with a future. It is the fourth most plentiful metal, and fortunately there is an abundance of it in the U.S.

Coal

            Our coal beds were formed about 300 million years ago. At that time large sections of the earth were low and swampy. The climate was warm and tropical. In these warm swamps grew huge plants, many of which are not on the earth today. Instead of big trees such as oaks and maples there were huge growths of ferns, horsetails, and mosses. Conditions in the warm, humid swamps favored the growth of plant life. When the plants dies, they fell into the water and were prevented from completely rotting and decaying. This went on for many, many years. Thick layers of plant remains were formed. The land was slowly sinking and the swamps became filled with water. Eventually, heavy layers of clay and sand that later hardened into rock were deposited over the plant remains. The pressure of the rocks, squeezing out gas and tar, changed the layers of plant remains into coal.
Kinds of Coal
Coal is a fossil fuel derived from vegetation. There are four broad classes of coal, depending on how much the original vegetation was changed. These are peat, lignite, bituminous, and anthracite. The carbon content increases through these stages: from 80% in wood to roughly 60% in peat, 70% in lignite, 85% in bituminous, and 95% in anthracite.
            Peat is a spongy substance of low heat (or carbon) content. It represents the first stage in the change of vegetation to coal. It is found in bogs in many parts of the world, particularly in Ireland where it is dried in the sun and used as a fuel.
            Lignite is a dark brown substance between peat and true coal. It is not a good fuel because of its low carbon content. In Europe it is used for making synthetic gasoline and is very satisfactory for this purpose. Enormous deposits of lignite, largely untapped, underlie parts of Wyoming, Montana, North Dakota, and Colorado.
            Bituminous is the most important variety of coal. It is soft and is widely used as a fuel. Its importance lies in the fact that when distilled, it gives off gases and tars that are used in many chemical industries.
            Anthracite, or hard coal, is almost solid carbon. For this reason it is relatively inactive chemically and is used only as a fuel; that is, its uses are limited to heating and cooking. Almost all the anthracite beds in the U.S. are in Northeastern Pennsylvania.

Coke is made from soft coal. Coke is used as a fuel, and enormous quantities of it are used in making steel. Coke is made by heating soft coal to a high temperature in airtight ovens. Gases and tarry substances are driven off, leaving the solid coke. The coal gases and tars are saved and used. Hundreds of valuable products, such as medicines, perfumes, and dyes, are obtained from coal tar. Most of the dyes used today are products of coal tar. Nylon is produced from coal, water, and air. Spun into thread which resembles silk, nylon is woven into fabrics for stocking, dresses, and other things.

Oil

            In 1859, Colonel Edwin L. Drake drilled the first oil well near Oil Creek, Pennsylvania. He struck oil at a depth of only 69 feet. Drake was interested in oil as a source of kerosene to replace the tallow candles which were then in use. After the automobile was invented, the demand for oil increased enormously.
            Today, oil furnishes power to planes, automobiles, ships, and locomotives. It is used to lubricate all kinds of machinery, and it is the raw material of vast chemical industries.
            Oil is usually a thick, dark-colored liquid. It is called petroleum. Petroleum was formed in the earth millions of years ago from tiny plants and animals that lived in shallow seas. These seas covered parts of the present land areas. The living things died and were buried in mud that settled to the ocean floor. In time this mud was covered with sand which later became rock. In some way, oil was formed from the buried remains of these plants and animals. Oil deposits are practically always found in sedimentary rocks of marine (sea) origin. These rocks are porous; that is, they have tiny holes, or pores, into which the oil moves. In some places the rocks were pushed up and formed pockets in the earth. In these pockets the oil eventually collected.
            When men seek oil, they search for places where sedimentary rocks are folded to form large pockets in the earth. There they drill through the earth, hoping to strike a pocket of oil. When oil is "struck," it may spout high into the air. Such a well is called a gusher. From most wells the oil must be pumped. It is pumped into large tanks and transported to refineries.
            Crude oil is a mixture of many compounds of carbon and hydrogen. At the refinery it is separated by distillation into different parts. The crude oil is run in pipes through a furnace where the heat changes it into several gases. These gases are changed back into liquid form in a large cooling tower. By regulating the temperature at which the different gases turn back to liquids, such products as gasoline, kerosene, fuel oil, and lubricating oils are separated.

Natural Gas

            Natural gas is found stored under great pressure in the earth, nearly always with petroleum. Like petroleum, it is obtained by drilling wells into the gas-bearing rock. Natural gas is an ideal fuel. It burns with a hotter flame than any of the other gaseous fuels. Found in more than half the states of the U.S., it is sometimes pumped hundreds of miles to cities where it is used for cooking. It may also be used for heating homes and as a fuel in manufacturing plants.

Rocks

            Some rocks of the earth are used in constructing homes and buildings.
            Granite is one of the most widely used building stones. It is very hard, is not affected by the weather, and will take a beautiful polish. It is frequently used for decorative purposes around buildings, for monuments, and as gravestones. If you visit a cemetery, you will probably see several granite monuments.
            Marble is a beautiful rock. It is not as durable as granite. Like limestone, it is fairly soft and is readily attacked by acids. It is frequently used for ornamental and decorative purposes. The fronts of public buildings and the stairways and corridors in large buildings are sometimes ornamented with marble. Like granite, marble is used for monuments and gravestones.
            Sandstones are good building stones. They are fairly durable and are affected much less by the weather than limestone and marble. Sandstones are red, brown, and gray, and are widely used for trimming and decorating buildings.
            Slate is familiar to every school boy and girl. The blackboards in many schoolrooms are made of slate. Slate was once mud at the bottom of the sea. First, the mud was changed to shale, a sedimentary rock; then by heat and pressure the shale was changed into slate, a metamorphic rock. Slate can be split into very thin layers, and is used for roofs, table tops, and stair treads.