There are so many precious things on the
earth but these ones are considered most precious. Your thought about the most
precious things of the earth differs from other people’s own. And what you
consider most precious might not actually be important to some people but these
lists have led to so many upheavals in the history of mankind.
1.
Oil
What would our world be
like without oil? We wouldn’t have gasoline-powered cars. We wouldn’t have
airplane fuel or oil to heat our homes. Many paints, fertilizers, and kinds of
cloth are made partly from oil. So are many plastics, chemicals, building
materials, and even medicines.
It’s hard to imagine life
without oil. Yet the world’s supply of this valuable resource is running out.
Oil is the purified form
of a black or brown liquid called crude oil. Crude oil is a mixture of
substances called hydrocarbons. They’re called hydrocarbons because they
are made up of the elements hydrogen and carbon. Hydrocarbons give off a lot of
energy when they burn. That’s why they make good fuels. They also can be
combined with other elements in many ways to make different products.
Crude oil forms under Earth’s
surface. It forms from the remains of sea animals and plants. (This is why oil
is called a fossil fuel—it comes from fossils.) When these living
things die, they sink to the sea bottom. Over millions of years, they form a
thick layer. The layer can get buried under sand and rock. Pressure and high
temperatures inside the planet change it into oil and natural gas.
Most crude oil is trapped
far underground. But it seeps through to the surface here and there, forming
pools of black liquid. People have known about these pools for thousands of
years. In the 1850s, chemists began to discover different ways crude oil could
be used. These discoveries set off a massive search for oil. This search is
still going on today.
2.
Gold
Gold Coins
Gold has been used as money since ancient times. The
metal is valuable because it is beautiful and easy to form into jewelry and
other objects.
“Gold! Gold! Gold!” screamed
the newspaper headlines. “Gold discovered in California!” That was in 1848. The
news brought 100,000 people rushing to California. They came seeking the yellow
metal that could make them rich.
People since ancient times
have used gold for jewelry and money. They used it in religious objects and
works of art. Wars have been fought over gold. And sometimes, as in California,
gold changed the course of history.
Gold is unusual among metals.
It does not rust or tarnish (grow dull and discolored). Gold coins
recovered from sunken treasures are still as shiny as when they sank.
Gold is soft enough to be
easily shaped into jewelry and other items. An ounce (31 grams) of gold can be
hammered into a sheet 16 feet (5 meters) on each side. It can be stretched into
a wire 62 miles (100 kilometers) long.
People find gold beautiful.
And it is rare. All the gold in the world would fit in a cube 65 feet (20
meters) on each side. Because it is so rare, its value doesn’t change much from
one year to the next. In ancient times, people could easily carry a lot of
wealth in the form of a small bag of gold.
3.
Diamond
Rough Diamond
Diamonds found in rocks are rough. Experts must cut and
polish them to make them into sparkling jewels.
They can cut metal. They
can cut glass. They are billions of years old and form deep within Earth. Some
are so rare and beautiful that people will pay a fortune to get one! They are
diamonds.
Diamonds are made of carbon,
a chemical element. That’s the same stuff that’s in the tip of a pencil. But
isn’t carbon soft, not hard?
Pencil carbon is so soft
that it rubs off on paper. But diamond carbon is so hard it can cut almost
anything. In fact, diamonds are the hardest things in nature. What makes the
difference? The atoms inside a diamond have a special crystal shape. This makes
them very hard.
Some diamonds can sparkle
brilliantly. Such diamonds are rare. They are precious and valuable, and people
wear them as jewelry. But most diamonds are small and contain flaws. These are
worth much less.
4.
Coal
Coal
Coal is a black rock made up of the element carbon. When
coal burns, it releases a large amount of energy as heat. Coal is used to fuel
power plants that produce electricity.
Let’s imagine for a moment
that there was no coal. Hey, who turned out the lights? And why isn’t the refrigerator
working, or the TV? Much of the electricity we use comes from coal.
Coal is a black rock. It
produces energy when it burns. The Chinese were mining and using coal for fuel
over 3,000 years ago. It once powered the world’s industry. It helped make the
United States a wealthy nation. Coal-burning trains carried people and products
across the country. Today, coal-burning power plants produce electricity for
many homes and businesses.
Coal is mostly made up of
the element carbon. When carbon burns, it releases a large amount of energy as
heat. That’s what makes coal such a useful fuel.
Coal is a fossil fuel.
That means it comes from the remains of ancient life buried deep in Earth’s
crust. The coal we use today started out as plants that grew in swamps millions
of years ago. When the plants died, they settled to the swamp bottom. Over
time, layers of mud and rock formed. They compressed and hardened the plant
material. Heat and pressure caused chemical changes. Gradually, the once-living
matter became coal.
5.
Copper
Copper-Coated Pennies
Most coins used the United States contain copper.
Pennies, shown here, are made of zinc with a thin coating of copper.
They actually have less copper than other U.S. coins!
Have you used anything copper
today? If you bought something and received change, there was copper in the
coins. Did you use any electrical devices? The electricity was carried to your
home by copper wires. There are even tiny amounts of copper inside you. Your
body needs it for digesting food and keeping your blood healthy.
Copper is a reddish-yellow metal.
When it’s found in pure form in the ground it’s called native copper. Usually,
though, copper is found combined with other elements in rocks. These rocks are
called copper ores.
When combined with other
elements, copper is often greenish in color. The Statue of Liberty is made
mostly of copper. Its greenish color comes from copper combined with the
element oxygen from the air.
Copper was one of the
first metals discovered by human beings. People were making tools and jewelry
from native copper over 10,000 years ago.
6.
Crystals
Snow Crystal
Snow is made up of tiny crystals of frozen water. All snow
crystals have six sides, but no two are exactly the same. Snowflakes form when
the crystals stick together.
Look closely at some table
salt through a magnifying glass. You’ll see that the bits of salt are made up
of tiny cubes. Each cube is a salt crystal. The salt crystals within the particles
can be different sizes, but they always have this shape.
A crystal contains identical
particles that are arranged in a particular pattern such as a cube, rectangle,
or hexagon. As a crystal grows in size, this pattern is repeated over and over.
Salt is made up of the
elements sodium and chlorine. Extremely tiny particles of sodium and chlorine,
called atoms, form a repeating cubic pattern in a crystal of table salt. The
more times the pattern is repeated, the bigger the crystal that forms.
7.
Fossils
Fossilized Ichthyosaur
Fossils are the remains of prehistoric plants or animals.
This fossilized ichthyosaur, a sea reptile that looked like a dolphin, dates
from about 185 million years ago.
Wading in chilly water under a
seaside cliff, you spot an odd piece of rock. You chip away at it before the
ocean tide comes in. When you get it home, you discover that you have found the
remains of an animal that no longer exists, a long-necked reptile with flippers
that lived in prehistoric seas.
Mary Anning probably had a day
like this in the early 1800s. Mary was one of the greatest fossil hunters of
all time. She found Plesiosaurus, Ichthyosaurus, and many other fossils.
She sold them to scientists to help support her family. Scientists in the early
1800s were just beginning to learn what fossils are and why they are important.
Fossils are the remains of
prehistoric plants and animals. Fossils can be leaves, bones, shells,
footprints, or even tiny bacteria.
Most fossils are in rock.
They form when a plant or animal gets buried in mud or sand at the bottom of a
lake, river, or ocean. Over thousands of years, the mud and sand turn into
rock.
8.
Gasoline
Oil Refinery
Gasoline is separated out from oil at a factory called an
oil refinery. This oil refinery is in California.
Gasoline makes cars run. This
liquid is very important to us. A car’s engine burns gasoline mixed with air.
The energy released by burning gasoline turns the car’s wheels and makes the
car go.
When the car starts to
run out of gas, it’s time to fill up the car’s gas tank at a gas station. When
you’re at a gas station, you’re probably standing on top of a huge underground
storage tank. The pump brings the gasoline up from the storage tank, and a hose
feeds it into the car’s gas tank.
Our world uses huge amounts
of gasoline. The United States alone uses about 310 billion gallons (1.2
trillion liters) every year.
Gasoline is one of many
substances found in oil, a natural liquid that forms deep underground. When
this crude oil is pumped out of the ground, it’s a mixture of substances called
hydrocarbons. They’re called hydrocarbons because they are made up of
chains of the elements hydrogen and carbon. Different hydrocarbons have chains
of different lengths.
Gasoline is a lightweight
liquid at room temperature, but it becomes a vapor (gas) when warmed up. When
gasoline vapor is mixed with oxygen from the air, a spark causes the mixture to
burn quickly and give off a lot of heat. That’s what makes gasoline a good
engine fuel. A car’s engine turns this heat into energy that turns the wheels.
9.
Gems
Jeweled Box
Gemstones are prized for their beauty and value. This
gold box is covered with precious jewels, including a rare citrine at the
center.
Jewelry in a store window
sparkles and shines. Beautiful polished stones called gems are set in
bracelets, necklaces, rings, and other jewelry. Diamonds, emeralds, rubies, and
sapphires are some popular gems that sparkle.
There is a gem called a
birthstone for every month of the year. A birthstone is a symbol of the month
when you were born. Do you know what your birthstone is?
Gems come in different colors.
Diamonds are clear. Rubies are red. Emeralds are green. Sapphires are blue.
Some gems have patterns or
different colors. You can see what looks like an eye in the gems called
tiger’s-eye and cat’s-eye. You see different colors in an opal when you move it
around.
10.
Minerals
Minerals in Rock
Rocks are made of one or more minerals. This piece of
granite contains the minerals feldspar (pink color), quartz (gray), and mica
(black).
Have you ever thrown a
rock? Ever seen a diamond ring? Ever added salt to your food? If you have, then
you’ve had a close encounter with minerals.
Minerals come mainly from
rocks. To be considered a real mineral, a substance has to occur naturally and
it has to come from inorganic material. Inorganic means not created by living
things. Oil and coal, for example, come from the remains of ancient plants. So
they’re not considered real minerals, at least by scientists.
But water is! It’s one of
only two minerals that naturally occur as a liquid. (The other is the liquid
metal mercury.) Think about that the next time you drink a glass of water:
You’re drinking a mineral!
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