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
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
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.
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.
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,
Lead. Solder, plumbing, car batteries, radiation shielding, printers'
type, pewter eating utensils and other objects, glass, ceramics, insecticides,
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 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.
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.
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
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 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.
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.
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 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 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.
is an alloy of copper and zinc.
silver contains zinc, copper, and nickel.
contains zinc, copper, and tin.
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."
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.
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
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.
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.
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
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
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.
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
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.
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.
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
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 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
Some rocks of the earth are used in constructing homes and buildings.
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.
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.
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.
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.