Download What is a mineral?

Chapter Introduction
Lesson 1 What is
a mineral?
Lesson 2 How are
minerals
identified?
Lesson 3 Sources and
Uses of Minerals
Chapter Wrap-Up
Mark Schneider/Getty Images
What is a mineral?
• A mineral is a naturally occurring,
inorganic solid with a definite chemical
composition and an orderly
arrangement of atoms or ions.
• There are approximately 4,000
minerals on Earth, but only about 30
are common.
What is a mineral? (cont.)
• Of the 30 common minerals, ten are
rock-forming minerals, including quartz,
feldspar, and olivine.
• These minerals occur naturally and are
not made in a laboratory.
What is a mineral? (cont.)
• Minerals have a definite chemical
composition.
• Some minerals, such as silver and
sulfur, are composed of just one
element. These are known as native
elements.
• Other minerals are made up of a
combination of several elements.
What is a mineral? (cont.)
• Minerals form predictable crystal
patterns.
• The internal arrangement of atoms or
ions determines the shape of a crystal.
What is a mineral? (cont.)
A crystal is a solid with a repeating
arrangement of atoms or ions in 3
directions.
What is a mineral? (cont.)
• Minerals are solids, meaning they
exhibit an orderly internal arrangement
of atoms or ions.
• Minerals are inorganic, or not from
biologic origins.
• Despite being inorganic, some
minerals can form as a result of
organic processes.
The Structure of Minerals
• Minerals occur in many different
shapes.
• When a crystal forms under the right
conditions and has time to grow, it will
develop a characteristic crystal shape.
• Most of the time, minerals grow in tiny
clusters.
The Structure of Minerals (cont.)
• The common rock-forming minerals are
composed of combinations of elements
that are abundant in Earth’s crust.
• Oxygen and silicon are the two most
abundant elements in the crust.
The Structure of Minerals (cont.)
• The two main families of rock-forming
minerals are the silicates and the
nonsilicates.
• A silicate is a member of the mineral
group that has silicon and oxygen in its
crystal structure.
• Nonsilicate minerals do not contain
silicon.
How do minerals form?
• All minerals form through crystallization.
• The process of crystallization occurs
when particles dissolved in a liquid or a
melt solidify and form crystals.
• The chemical and physical properties of
minerals can help geologists infer the type
of environment where these minerals
formed.
How do minerals form? (cont.)
• Minerals can crystallize from either hot
or cool solutions.
• As water evaporates from a cool
solution in a dry environment, solids
crystallize out of the water and form
minerals.
• Sometimes minerals can crystallize
from water in environments that aren’t
dry.
How do minerals form? (cont.)
• Hot solutions are made when water
flows through cracks in the crust into
deep and hot environments.
• Sometimes hot solutions carry large
concentrations of dissolved solids that
eventually become valuable mineral
deposits.
How do minerals form? (cont.)
• Minerals can also form from magma.
Magma is molten material stored
beneath Earth’s surface.
• When magma erupts on or near Earth’s
surface, it is called lava or ash.
How do minerals form? (cont.)
• As lava or ash cools above ground or
magma cools underground, atoms and
ions arrange themselves and form
mineral crystals.
• Small crystals form as lava cools
quickly on or near Earth’s surface and
large crystals sometimes form as
magma cools and crystallizes slowly
below Earth’s surface.
How do minerals form? (cont.)
• Minerals that form deep within Earth’s
crust and mantle are stable under high
pressure and high temperature
conditions.
• Metamorphic activity can uplift minerals
from great depths onto Earth’s surface.
• Changes in pressure and temperature on
Earth’s surface combined with agents of
erosion can cause minerals to break
down and eventually form new minerals.
Physical Properties
• Mineralogists are scientists who study
the distribution of minerals, mineral
properties, and their uses.
• Scientists use the physical and
chemical properties of minerals to learn
a mineral’s identity and classify
unknown minerals.
Physical Properties (cont.)
• Color alone cannot be used for mineral
identification because many different
minerals can be the same color.
• Variations in color reflect the presence
of different types of chemical
impurities, such as iron, chromium, or
manganese.
Physical Properties (cont.)
• The way a mineral reflects or absorbs
light at its surface is called luster.
• Minerals that are also
metals, such as copper,
silver, and gold, reflect
light and produce the
shiniest luster, called
metallic luster.
DEA/A.RIZZI/Getty Images
Physical Properties (cont.)
• Luster is directly related to the
chemical composition of minerals.
• Streak is the color of a mineral in
powdered form.
• Streak is only useful for identifying
minerals that are softer than porcelain.
• Nonmetallic minerals generally
produce a white streak.
Physical Properties (cont.)
• Many metallic minerals produce
characteristic streak colors.
• Hardness is the resistance of a
mineral to being scratched.
• Friedrich Mohs developed the Mohs’
hardness scale to compare the
hardness of different minerals, with
scale ranging from 1 to 10.
Physical Properties (cont.)
• Sometimes the way a mineral breaks
provides clues to its identity.
• The arrangement of atoms or ions and
the strengths of their chemical bonds
determine how a mineral breaks.
• Minerals break where bonds between
atoms or ions are weak.
Physical Properties (cont.)
• If a mineral breaks with smooth, flat
surfaces, it has cleavage.
• If a mineral breaks and forms uneven
surfaces, it has fracture.
Physical Properties (cont.)
• The density of a mineral is also helpful
in identifying it. The density of an
object is equal to its mass divided by
its volume.
• Some minerals have special
properties, such as texture, odor,
fluorescence, magnetism, or the way
they react when they come in contact
with hydrochloric acid.
Minerals are valuable resources used to
construct many parts of a home.
Mineral Resources
• Rock that contains high enough
concentrations of a desired substance
that it can be mined for a profit is called
an ore.
• Ores of the elements iron (Fe) and
aluminum (Al) are among the most
abundant of the metallic mineral
resources used every day.
Mineral Resources (cont.)
• Aluminum is abundant in Earth’s crust
but rarely occurs as a native element.
• Gold occurs in a ration of 1 part gold to
4 billion parts rock in Earth’s crust, but
in large enough concentrations to be
mined for profit.
• The technology industry is dependent
upon metallic mineral resources like
platinum.
Mineral Resources (cont.)
Humans use
nonmetallic minerals
that are not ores,
such as the raw
materials used for
road construction,
building stone, and
fertilizers.
Construction site: Sascha/Photonica/Getty Images
Limestone block: Joel Sartore/National Geographic/Getty Images
White gravel: Mark Harwood/Getty Images
Sand: Siede Preis/Getty Images
Mineral Resources (cont.)
• A gemstone is a rare
and attractive mineral
that can be worn as
jewelry after it is cut
and polished.
Mineral Resources (cont.)
• The physical properties of gemstones
also make them useful in industry.
• Sometimes human-made gems are
less expensive than the same natural
gems.