Chapter 4 Section 2
Rock and Mineral Resources
How Are Rocks Different
from Minerals?
A mineral is a naturally formed, inorganic solid that
forms crystals and is always made of the same elements.
Let’s look at each part of this definition more closely.
• Minerals form naturally. For example, most diamonds
form far underground. These diamonds are minerals.
However, some diamonds are made by people. These
diamonds are not minerals, because they did not form
naturally.
• Minerals are solids. For example, frozen water, or ice,
in a glacier is considered a mineral because it is solid.
However, liquid water in a stream is not a mineral.
• Minerals form by inorganic processes. In other words,
they are not formed from living things. For example, coal
is not a mineral because it forms from the remains of
plants.
• Minerals are crystals. Crystals are solids whose particles
are lined up in a repeating pattern. For example, volcanic
glass is not a mineral because the particles in it are not
lined up in a pattern.
• Minerals are always made of the same elements. For
example, every sample of the mineral fluorite contains
the same elements: calcium and fluorine. In many cases,
the elements in minerals are valuable natural resources.
A rock is a natural material that makes up most of the
solid part of Earth. Most rocks are made from one or more
minerals. Rocks can also be made from solid materials that
are not minerals. For example, a rock can contain coal or
volcanic glass, neither of which are minerals.
How Do Minerals Form?
Minerals form in many different ways. The table below
shows five ways that minerals can form.
Process Description Examples of
minerals that form this way
1)Evaporation
When a body of salt water dries up,
minerals are left behind.
gypsum, halite
2)Metamorphism
High temperatures and pressures deep
underground can cause the minerals in
rock to change into different minerals.
garnet, graphite,
magnetite, talc
3)Deposition
When water carries dissolved materials
into lakes and seas, minerals form and
sink to the bottom.
calcite, dolomite
4) Reaction
Water underground can be heated by
hot rock. The hot water can dissolve
some minerals and deposit other
minerals in their place.
gold, copper,
sulfur, pyrite,
galena
5)Cooling
Melted rock can cool slowly under
Earth’s surface. As the melted rock
cools, minerals form.
mica, feldspar,
quartz
How Are Minerals Removed from Earth?
People mine many kinds of rocks and minerals from
the ground and make them into objects we need. Some
kinds of rocks and minerals have more useful materials
in them than others. An ore is a rock or mineral that
contains enough useful materials for it to be mined at a
profit.
There are two ways of removing ores from Earth:
surface mining and subsurface mining. The type of
mining that people use depends on how close the ore is
to the surface.
SURFACE MINING
People use surface mining to remove ores that are
near Earth’s surface. Open-pit mining is used to remove
gold and copper from the ground. Explosives break up
the overlying rock and ore. Then, trucks haul the ore
from the mine to a processing plant.
Quarries are open mines that are used to remove
sand, gravel, and crushed rock. The layers of rock near
the surface are removed and used to make buildings and
roads.
Strip mines are often used to mine coal. The coal is
removed in large pieces. These pieces are called strips.
SUBSURFACE MINING
People use subsurface mining to remove ores that are
deep underground. Iron, coal, and salt can be mined in
subsurface mines.
RESPONSIBLE MINING
Mining can help us get the resources we need, but it
can also create problems. Mining may destroy or harm
the places where plants and animals live. The wastes
from mining can be poisonous. They can pollute water.
One way to reduce these problems is to return the land
to its original state after mining is finished. This is called
reclamation. Since the mid-1970s, laws have required
the reclamation of land used for mining. Another way
to reduce the problems with mining is to use less of the
What Are Rocks and Minerals Used For?
The table shows how some common minerals
are
used.
 Mineral Uses
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Copper electrical wire,
plumbing, coins
Gypsum wallboard, plaster,
cement
Diamond jewelry, cutting
tools,
drill bits
Halite table salt, road salt,
water softener
Galena lead in batteries,
ammunition
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Quartz glass, silicon for
computer chips
Bauxite aluminum cans, foil,
appliances, utensils
Silver photography,
electronic products,
jewelry
Gold jewelry, computers,
spacecraft, dentistry
Sphalerite zinc for jet aircraft,
paints
METALS
Many minerals contain metals. Many of the features
of metals make them useful in aircraft, automobiles,
computers, and spacecraft. Some of these features are
listed below.
• Metals have shiny surfaces.
• Light cannot pass through metals.
• Heat and electricity can pass through metals easily.
• Metals can be rolled into sheets or stretched into
wires.
Some metals react easily with air and water. For
example, iron can react with oxygen in the air to
produce rust. Other metals do not react very easily. For
example,gold does not react with very many chemicals.
Therefore, it is used in many spacecraft.
NONMETALS
Many minerals also contain nonmetals. Some
important features of nonmetals are listed below.
• Nonmetals have shiny or dull surfaces.
• Light can pass through some kinds of nonmetals.
• Heat and electricity cannot pass through nonmetals easily.
Nonmetals are very important. For example, the
mineral calcite is used to make cement. Sand is made
of small pieces of rocks and minerals. It contains silica,
which is used to make computer chips and glass.