and cleavage. They may also use other
Salt is a common mineral. Salt can be gathered
from salt flats, or dried-up lakes where
salt has been left behind.
BRITANNICA STUDENT ENCYCLOPEDIA Mineral 131
tests, including how the mineral reacts
to electricity or magnets.
Minerals come in many different colors.
They also reflect light in different ways.
Some are transparent, or see-through.
Others are iridescent, which means that
their color changes as light hits them
from different directions.
Mineralogists describe a mineral’s hardness
with the Mohs scale. The scale lists
10 typical minerals, from the softest
(talc) to the hardest (diamond). A mineral
can be identified by comparing its
hardness to the hardness of these 10
minerals.
The cleavage of a mineral is the way it
splits or breaks. Mica, for example,
breaks into thin, flat sheets.
Uses
Animals and plants need minerals to
live. For example, humans need the
mineral calcium to develop healthy
bones and teeth. Animals, including
humans, get minerals from plants or
from the milk, eggs, and meat of planteating
animals. Most plants get the minerals
they need from soil.
People also use minerals to make buildings,
machines, tools, cleaning products,
cosmetics, jewelry, and many other
items. Digging useful minerals out of
the ground is called mining.
#More to explore
Metal • Mining • Rock • Sand • Soil
Minerva
#see Athena.
Mining
Earth’s crust contains many minerals
and other materials that are useful to
people. To get these valuable natural
resources, people must dig into the
ground. The holes that they dig are
called mines. Some mines are narrow
shafts, or tunnels, that go very deep
underground. Other mines are large
open pits, like canyons. The people who
work in mines are called miners.
People dig mines to get such things as
diamonds, coal, silver, salt, and many
other materials. When a mine provides
stone for building, it is called a quarry.
Drilling into Earth for petroleum, or oil,
is another special type of mining. In this
case, the hole in the ground is called a
well, not a mine.
Mohs Hardness Scale
Hardness Mineral
softest 1 talc
2 gypsum
3 calcite
4 fluorite
5 apatite
6 orthoclase
7 quartz
8 topaz
9 corundum
hardest 10 diamond
Example: A certain mineral can be scratched
by topaz but not by quartz. Therefore, it is
softer than topaz and harder than quartz. It
has a Mohs hardness of between 7 and 8.
132 Minerva BRITANNICA STUDENT ENCYCLOPEDIA
Making Mines
There are many ways to make a mine.
One way is by digging underground
tunnels. Another way is by removing top
layers of soil and rock to create a pit.
Tunnel mines can stretch for miles
underground. Sometimes the tunnels
open into large rooms. Miners who
work deep underground in these rooms
use large machines to dig away at the
walls. Fresh air, water, and electricity
must be lowered down to them from
aboveground.
Workers use large earth-moving
machines to make pit mines. The
machines scrape and dig at the soil until
they uncover the minerals. As the
machines dig deeper and deeper, they
create a huge hole in the ground.
Sometimes miners must use explosives,
such as dynamite, to create tunnels or to
break up Earth’s hard surface. These
explosions also break the materials into
smaller pieces so that they are easier to
collect.
Dangers of Mining
Mining is dangerous work. Tunnel
mines can cave in or quickly flood with
water. When such disasters happen,
miners may be trapped belowground.
The explosions used in mining can also
release poisonous gases.
History
People have dug mines since prehistoric
times. Hundreds of thousands of years
ago, during the Stone Age, people dug
in the ground to search for flint. Flint is
Miners drill for gold in a mine in South
Africa.
Miners may go into underground tunnels to
dig for ore (rock containing valuable minerals).
Or they may dig ore out of large pits
in the ground.
BRITANNICA STUDENT ENCYCLOPEDIA Mining 133
a stone that can be used to make weapons
and tools.
The first metal to be mined was copper.
The oldest copper mines are in Egypt.
Ancient Egyptians dug these mines
about 7,000 years ago. By 5,000 years
ago, people were also mining tin and
combining it with copper to create
bronze. This metal was important for
making sturdy, long-lasting weapons and
tools. Later peoples mined iron to make
even stronger tools and weapons.
The ancient Greeks mined (quarried)
marble for many beautiful buildings.
The ancient Romans had huge mining
operations, many in lands that they conquered.
During the 1400s and 1500s the
Spanish grew rich by mining gold and
silver in the Americas.
The first mining operations in what is
now the United States started in the
1700s. Meanwhile, in Great Britain coal
mining helped to start the Industrial
Revolution. This was a time when
people began to use machines to make
goods in factories. Coal was an important
source of power for operating the
machines.
In the 1900s many countries worked to
make mining safer for miners. Today
many people are concerned about pollution
and other damage to the environment
caused by mining.
#More to explore
Bronze • Coal • Iron • Mineral
• Petroleum • Quarrying
Mink
