Download Minerals

Table of Contents
Chapter: Earth Materials
Section 1: Minerals
Section 2: Igneous Rocks
Section 3: Sedimentary Rocks
Section 4: Metamorphic Rocks and
the Rock Cycle
Minerals
1
Common Elements
Composition of Earth’s Crust
• The crust is the outermost layer of Earth.
Minerals
1
What’s a Mineral?
• A mineral is a naturally occurring
element or compound that is inorganic,
solid, and has a crystalline structure.
Minerals
1
Physical Properties
• A mineral has a characteristics set of
physical properties, but some of these
properties can differ from sample to
sample.
Minerals
1
Atom Arrangement
• Some physical properties are controlled
by the orderly arrangement of atoms in
a mineral’s structure.
• The arrangement of atoms and the
bonds between them can reflect the
way a mineral breaks, how hard it is,
and what types of crystal shape it has.
Minerals
1
Atom Arrangement
• Minerals break along planes that cut across
relatively weak chemical bonds, a smooth, flat
surface is created. This is called cleavage.
• Some minerals do not split along well-defined
flat surfaces. In such cases, a mineral will
break unevenly. This type of irregular break is
called fracture.
Minerals
1
Hardness
• The physical property that measures resistance
to scratching is called hardness.
Minerals
1
Luster and Streak
• The way a mineral reflects light is the physical
property known as luster.
• Metallic and nonmetallic.
• Metallic luster minerals reflect light in a way
that a metal surface might.
Minerals
1
Luster and Streak
• Nonmetallic luster, includes minerals that
shine like glass or appear earthy or waxy.
• The color of mineral in powdered form is
called streak.
Minerals
1
Crystal Shape
• The orderly internal arrangement of
atoms in a mineral often is indicated
by its external crystal shape.
• The types of symmetry
shown by the crystal
are key elements in
determining the crystal
system to which a
mineral belongs.
Minerals
1
Mineral Formation
• Growth also is controlled by how fast
atoms can migrate to the crystal and by
the temperature and pressure conditions
of the surroundings.
Minerals
1
Minerals From Hot Water
• Some minerals are produced from hot water
solutions rich in dissolved mineral matter.
• When hot water passes through cracks
in cooler rock, minerals may form
within the cracks.
Minerals
1
Minerals from Magma
• Molten rock material found inside Earth
is called magma.
• As magma cools, atoms slow down and
begin to arrange into an orderly structure.
• Below the solidification temperature
of a mineral, crystals of that particular
mineral may form and grow.
Minerals
1
Minerals From Evaporation
• When water slowly evaporates, concentrated
dissolved mineral may be left behind to form
crystal.
Minerals
1
Mineral Groups
Silicates
• Silica is a
common term for
a compound that
contains silicon
plus oxygen or
silicon dioxide
(SiO2).
Minerals
1
Silicate Structures
• The simplest silicate structures have siliconoxygen tetra-hedrons that are not linked
together.
• By joining silicon-oxygen tetrahedrons
together, chains, sheet, and threedimensional framework structures can form.
Minerals
1
Silicate Structures
• Quartz and feldspar group silicates make up
most of Earth’s continental crust.
• Earth’s oceanic crust is denser and contains a
larger percentage of silicates whose
tetrahedrons are not linked together as much.
Minerals
1
Important Non-silicates
• Many important mineral groups are
not silicates.
• These include the carbonates, oxides,
halides, sulfides, sulfates, and native
metals.
• The non-silicate groups are a source of
many valuable ore minerals and building
materials.
Minerals
1
Important Non-silicates
• To be an ore, a mineral must occur in large
enough quantities to be economically
recoverable.
Section Check
1
Question 1
Which is NOT a mineral?
A. apatie
B. flourite
C. gold
D. oxygen
Section Check
1
Answer
The answer is D. A mineral must be a solid.
Section Check
1
Question 2
Which is NOT a physical property of minerals?
A. cleavage
B. fracture
C. hardness
D. Mohs
Section Check
1
Answer
The answer is D. Mohs is a scale used to
determine the hardness of a mineral.
Section Check
1
Question 3
How many crystal shapes have been identified?
A. five
B. six
C. seven
D. eight
Section Check
1
Answer
The answer is B. Minerals can be classified by
these six shapes.
Igneous Rocks
2
What’s a rock?
• A rock is a naturally formed consolidated
mixture containing minerals, rock fragments,
or volcanic glass.
• Rocks are identified by their composition
and texture.
• Texture is a description that includes
the size and arrangement of the rock’s
components.
Igneous Rocks
2
Intrusive Igneous Rocks
• Igneous rocks are those that form from
molten rock material called magma.
• Such rocks also are called intrusive
igneous rocks because they form within,
or push into, regions of Earth’s crust.
Igneous Rocks
2
Nature of Magma
• As it passes through rock, magma might
cause partial melting of the rock it intrudes.
• Geologists have learned that minerals melt at
different temperatures, so some will melt
when exposed to the thermal energy of the
magma.
Igneous Rocks
2
Nature of Magma
• As crystals solidify in cooling magma, they
use up certain atoms.
• Hightemperature
magmas
tend to
crystallize
first.
Igneous Rocks
2
Nature of Magma
• Late-forming, less dense minerals tend
to solidify at
lower
temperatures
and float to
the top of
the magma
chamber.
Igneous Rocks
2
Nature of Magma
• The composition of intrusive igneous
rocks gives you clues as to where in
Earth they formed.
• Igneous rocks with abundant quartz
generally are associated with continental
crust.
• Those with little or no quartz generally
are associated with deep locations in
continental crust or with oceanic crust.
Igneous Rocks
2
Intrusive Igneous Rock Texture
• In intrusive igneous rocks, grain size, which
means the size of individual mineral crystals,
gives you clues as to how fast magma
cooled.
• Magma that cools slowly, allows atoms time
to migrate about and form large crystals.
Igneous Rocks
2
Classification of Intrusive
Igneous Rocks
• Rocks that are quartz-rich and contain
potassium feldspar and plagioclase feldspar
are called granite.
• Rocks with no quartz and abundant plagioclase
feldspar and pyroxene are called gabbro.
• Peridotite is denser than gabbro, is composed
mainly of olivine and pyroxene.
Igneous Rocks
2
Extrusive Igneous Rocks
• Extrusive igneous rocks are those that cool
from lava that has erupted at Earth’s surface.
• These rocks may have the same compositions
as intrusive igneous rocks, but they always
will have different textures.
• Composition of the surrounding rock material
will also affect the extrusive magma.
Igneous Rocks
2
Extrusive Igneous Rock
Composition
• A magma rich in silica (SiO2) forms rhyolite
if it cools rapidly.
• Similarly, gabbro’s fine-grained volcanic
counterpart is basalt, which is a common
rock in Earth’s oceanic crust.
Igneous Rocks
2
Extrusive Igneous Rock
Composition
Igneous Rocks
2
Extrusive Igneous Rock
Textures
• If cooling starts off slowly below the
surface with large crystals, but then finishes
at a faster rate to form small or no crystals,
the extrusive rock is called porphyry.
Igneous Rocks
2
Effect of Gases
• A texture called vesicular forms near the
top surface of a flow where gases escape.
Section Check
2
Question 1
What might you expect to find if you examined
a rock under a microscope?
Answer
A rock is a naturally formed consolidated
mixture containing minerals, rock fragments,
or volcanic glass.
Section Check
2
Question 2
Igneous rocks form from molten rock material
called _______.
A. basalt
B. silica
C. magma
D. granite
Section Check
2
Answer
The answer is C. There are two types of
igneous rocks; intrusive and extrusive.
Section Check
2
Question 3
Extrusive igneous rocks form when _______
cools.
A. lava
B. magma
C. water
D. volcanic glass
Section Check
2
Answer
The answer is B. When magma reaches Earth’s
surface it is called lava.
Sedimentary Rocks
3
Rocks From Surface Materials
• Rock is a consolidated mixture of
minerals. Some of these minerals could
be in bits and pieces of other rocks. Such
small bits and pieces are called clasts.
• Rocks inside Earth are protected from
surface conditions.
• Rock exposed at the surface is attacked
by the weather.
Sedimentary Rocks
3
Transportation and Deposition
• Mechanical weathering processes break
into smaller clasts.
• When clasts are transported
to new locations, they often
become rounded before
being deposited.
• When clasts are loose on Earth’s surface, they
don’t fit together perfectly. The empty space
in between the grains is called porosity.
Sedimentary Rocks
3
Transportation and Deposition
• When buried by more
sediment deposited above
them, clasts can be smashed
together with such great
force that they become
compressed and stick
together.
• This process is called compaction.
Sedimentary Rocks
3
Transportation and Deposition
• Water moving between clasts carries dissolved
minerals that can act as cement. This process
is called cementation.
• Most of the time both
compaction and
cementation work
together to make
sedimentary rock.
Sedimentary Rocks
3
Detrital Sedimentary Rock
• Detritus is another name given to clasts.
• Clasts can come in many sizes.
• In order of decreasing size, clasts are
known as gravel, sand, silt, or clay.
Sedimentary Rocks
3
Detrital Sedimentary Rock
• Geologists have found
that size works well as
a clue to the kind of
environment in which
a rock formed.
• It takes more force, or
energy, to lift or move
gravel than it does to
lift or move sand.
Sedimentary Rocks
3
Detrital Sedimentary Rock
• Detrital sedimentary
rock composition
depends on sources
to rock material that
were eroded,
transported, and
eventually deposited.
Sedimentary Rocks
3
Detrital Sedimentary Rock
• Some minerals tend to be more common in
detrital sediments because they are harder
or more resistant to being dissolved.
• Geologists examine sedimentary rock
compositions and try to reconstruct what
happened to form them.
• The general rock name is determined by the
clast size.
Sedimentary Rocks
3
Detrital Sedimentary Rock
• Clast size also provides clues to help
determine the deposition environment of
the sediment that formed the detrital rock.
Sedimentary Rocks
3
Chemical Sedimentary Rocks
Precipitation
• If water receives more dissolved materials
than it can hold in solution, then the
excess must precipitate out as microscopic
crystals.
Evaporation
• The other option is for some water to evaporate.
• This leaves an oversupply of dissolved matter
and again crystals.
Sedimentary Rocks
3
Biochemical Sedimentary Rocks
• If sedimentary rocks contain the remains
of living organisms they are called
biochemical sedimentary rocks.
• Limestone is composed, of the remains of
marine organisms that had hard parts made
of calcium carbonate.
• Coal is sedimentary rock composed almost
entirely of the carbon that remains after
plant material is compressed underground.
Sedimentary Rocks
3
Biochemical Sedimentary Rocks
• Coal goes through a
series of changes as it
forms from peat.
• Each stage of compaction
drives out more impurities
and leaves behind a more
concentrated form of
carbon.
Section Check
3
Question 1
Small bits and pieces of rock are called _______.
A. clasts
B. fragments
C. pebbles
D. pieces
Section Check
3
Answer
The answer is A. The word clast is from the
Greek klastos which means “broken.”
Section Check
3
Question 2
Which is NOT a type of clast?
A. clay
B. gravel
C. sediment
D. silt
Section Check
3
Answer
The answer is C. The four types of clasts are
gravel, sand, silt, and clay. Sediment can
contain any of these types of clasts.
Section Check
3
Question 3
_______ is a type of biochemical sedimentary
rock that humans use to make electricity.
A. Coal
B. Limestone
C. Gypsum
D. Quartz
Section Check
3
Answer
The answer is A. Coal is composed almost
entirely of carbon.
Metamorphic Rocks and the Rock Cycle
4
Metamorphic Rocks
• Metamorphic rocks, have been changed
by some combination of thermal energy,
pressure, and chemical activity.
• Any igneous, sedimentary, or metamorphic
rock is subject to change through
metamorphism.
Metamorphic Rocks and the Rock Cycle
4
Metamorphic Rock Composition
Changing Minerals
• Clay minerals tend to form micas with
increasing metamorphic conditions.
• Some new minerals form by dehydration
at higher temperature and pressure.
Metamorphic Rocks and the Rock Cycle
4
Changing Minerals
• Deep burial or regional movements of
large parts of Earth’s crust and uppermost
mantle cause regional metamorphism.
• Local contact of any preexisting rock with
magma is called contact metamorphism.
Metamorphic Rocks and the Rock Cycle
4
Changing Minerals
• Foliated textures in
metamorphic rocks have
lots of layers or bands.
• Nonfoliated metamorphic
textures include rocks
whose grains are in more
random orientations.
Metamorphic Rocks and the Rock Cycle
4
Foliated Rocks
• The most common sedimentary rocks
in Earth’s crust are mudrocks.
• These
rocks
contain
abundant
clay
minerals.
Metamorphic Rocks and the Rock Cycle
4
Foliated Rocks
• Nonfoliated metamorphic rocks tend to have
random crystal orientation and uniform grain
size.
• Mineral grains tend to grow as the grade of
metamorphism increases.
Metamorphic Rocks and the Rock Cycle
4
Metamorphic Rock Classification
• Much like other rock types, metamorphic
rocks can be classified based on texture and
composition.
Metamorphic Rocks and the Rock Cycle
4
Metamorphic Rock Classification
• Mineral composition provides clues about
the original rock type before metamorphism,
and indicates to what degree a rock had been
metamorphosed.
Metamorphic Rocks and the Rock Cycle
4
The Rock Cycle
• Processes of the rock cycle include any
chemical and physical conditions that
continuously form and change rocks.
Section Check
4
Question 1
Which is NOT an agent of metamorphism?
A. chemical activity
B. pressure
C. thermal energy
D. wind
Section Check
4
Answer
The answer is D. Wind is responsible for erosion
on some rocks but it does not help form them.
Section Check
4
Question 2
Describe foliated metamorphic rocks.
Section Check
4
Answer
Foliated textures in metamorphic rocks have
lots of layers or bands in them.
Section Check
4
Question 3
Is there a beginning and end to the rock cycle?
Answer
No, the rock cycle is a continual process in
which rocks change from one form to another.
Help
To advance to the next item or next page click on any
of the following keys: mouse, space bar, enter, down or
forward arrow.
Click on this icon to return to the table of contents.
Click on this icon to return to the previous slide.
Click on this icon to move to the next slide.
Click on this icon to open the resources file.
Click on this icon to go to the end of the presentation.
End of Chapter Summary File