The best-known irises are the common
garden irises. They are also called
bearded irises. This is because each of
the falls has a fuzzy growth that looks
something like a beard. Bearded irises
grow from rhizomes. They have stiff,
swordlike leaves and long stems. They
can grow to 3 feet (90 centimeters) tall.
They usually have a strong fragrance.
#More to explore
Flower • Garden
Iron
Iron is the most widely used metal on
Earth. Iron is used to make steel. In
turn, steel is used to make buildings,
bridges, railroad tracks, vehicles of all
kinds, and countless other products.
The Siberian iris grows in central
and eastern Europe. Its flowers
may be violet-blue or white.
People make some decorative railings out of
iron.
BRITANNICA STUDENT ENCYCLOPEDIA Iron 157
Iron in Earth’s Crust
Iron is the second most common metal
in Earth’s crust. Of the metals in the
crust, only aluminum is more common.
Iron is also the fourth most common
element (basic substance) in the crust.
Iron in its pure form is a heavy, silvery,
magnetic metal. But iron is almost never
found in its pure form in nature.
Instead, it is found in the form of iron
ores. Ores are minerals with mixtures of
different elements. The main iron ores
are made up of iron linked to oxygen or
to oxygen and carbon.
Separating and Using Iron
Workers separate pure iron from iron
ore by a process called smelting. Smelting
involves heating iron ore to a very
high temperature. As the iron ore melts,
the pure iron separates from the ore.
Hot lumps of iron may be pounded into
shapes. Melted iron may be poured into
molds of different shapes. As the iron
cools, it hardens. Today, however, most
iron is made into steel. Steel is a mixture
of iron and carbon. Steel is stronger than
iron alone.
Thousands of years ago people may have
gotten iron from iron meteorites. Meteorites
are chunks of rock that fall to
Earth from outer space. After ancient
peoples discovered how to smelt iron,
they learned how to make iron tools and
weapons. During a period called the
Iron Age, the knowledge of how to use
iron spread across Europe and Asia.
Iron in the Body
Iron is an important part of a person’s
diet. Good sources of iron are red meat,
chicken, tuna, egg yolks, beans, whole
grains, dried fruit, and leafy green vegetables.
The body uses iron to build a
substance called hemoglobin in the
blood. Hemoglobin carries oxygen to all
the cells in the body. The cells use the
oxygen to release the energy they need
to do their jobs.
#More to explore
Iron Age • Metal • Steel
Iron Age
The Iron Age was a time in early human
history when people began to use tools
and weapons made of iron. The Iron
Age started and ended at different times
in different places. The earliest Iron Age
probably took place in the Middle East
Iron pounded
into a shape is
called wrought
iron. Iron
poured into a
mold is called
cast iron.
People in eastern Europe made iron tools
more than 2,400 years ago.
158 Iron Age BRITANNICA STUDENT ENCYCLOPEDIA
and southeastern Europe. It started there
in about 1200 BC.
Background
The earliest human beings lived during
the Stone Age. Stone Age peoples made
tools and weapons of stone. Later they
learned to make tools and weapons from
copper and from bronze, which is a mixture
of copper and tin. This time was
known as the Bronze Age. The Iron Age
started after people learned to remove
iron from rock using a very hot fire. Iron
was better than bronze for tools and
weapons because it was harder and
stronger.
Events of the Iron Age
The knowledge of how to get iron from
rock and how to make iron tools spread
quickly from the Middle East to Egypt
and Greece. The Iron Age eventually
spread as far asWest Africa, northern
Europe, India, and East Asia. Australia
and the Americas did not have an Iron
Age. European settlers brought ironworking
to those places much later.
The use of iron brought important
changes to people’s lives. People used
iron to make strong tools, which made
farming easier. They also made iron
swords and other weapons. Huge armies
of soldiers soon carried iron weapons.
These weapons made an army much
harder to defeat. Armies traveled to
other lands and took over places they
liked. Kings and other rulers gained
great power.
Other changes in technology also happened
during the Iron Age. People built
large forts and bridges. Pottery and
weaving improved. Humans dug deep
mines in the ground to find salt and
other valuable minerals.
End of the Iron Age
The Iron Age came at the end of prehistory,
or the time before humans used
writing. (In some places people were
already using early forms of writing
when the Iron Age began.) The Iron Age
ended as writing became widespread and
as civilization grew more complex.
Still, iron was the most important metal
until the 1800s. People had often mixed
iron with other materials to make it
stronger, but in the 1800s they learned
easier ways to do this. As a result steel (a
mixture of iron and carbon) became
more widely used than iron alone.
#More to explore
Bronze Age • Iron • Prehistoric Life
• Stone Age
A museum in Great Britain shows the type
of house that people built in about 300 BC,
