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Earth’s Matter
Minerals and Rocks
Lesson 2.1 - Properties of Minerals
For a substance to be a mineral, it must have all five of these
characteristics
1.
2.
3.
4.
5.
occurs naturally
can form by inorganic processes (not part of living thing)
has a crystal structure
has a definite chemical composition
and is a solid
Minerals, Compounds,
and Elements
● Almost all minerals are compounds
● Remember compounds are made of two or more
elements bonded together
● Example: Quartz - one atom of silicon for every two atoms
of oxygen
● Some elements occur in nature in a pure form: copper,
silver and gold which are minerals as well.
How are minerals identified?
Each mineral has characteristic properties that can be used
to identify it.
● color, streak, luster, hardness, density, crystal structure,
cleavage, fracture, and special properties (bend light,
glow, conduct electricity)
How are minerals formed?
In general, minerals can form in three ways.
● from organic processes. (clam shells)
● crystallize from materials that are dissolved in solutions.
● as magma and lava cools.
Lesson 2.2 - Classifying Rocks
How do geologists classify rocks?
● To study a rock sample,
geologists observe the rock’s
mineral composition, color, and
texture.
● Rocks are made of mixtures of
minerals and other materials.
About 20 minerals make up
most of the rocks of Earth’s
crust.
Mineral Composition and Color
● A rock’s color provides clues to the rock’s mineral
composition.
● For example, granite is generally a light-colored rock that
has high silicon content. Basalt is a dark-colored rock that
has a lower silicon content.
Texture
● Most rocks are made
up of particles of
minerals or other
rocks, which
geologists call
grains.
● Grains give the rock
its texture. Texture is
the look and feel of a
rock’s surface.
Origin
● There are three groups of rocks that form in different
ways.
○ Igneous rock forms from cooling magma or lava.
○ Most sedimentary rock forms when small particles of
rocks or organic remains are pressed and cemented
together.
○ Metamorphic rock forms when a rock is changed by
heat, pressure, or chemical reactions.
Lesson 2.3 - Igneous Rocks
How Do Geologists Classify Igneous
Rocks?
● All igneous rocks form from magma or
lava
● However they can look vastly different
from each other
● Classified by their origin, texture, and
mineral composition. (see a pattern
forming)
● It may form on or beneath Earth’s
surface.
Extrusive - from
lava that erupted
onto surface.
(exited Earth)
Intrusive - from
magma hardening
beneath surface.
(inside Earth)
How Are Igneous Rocks Used?
● People throughout history have used igneous rock for
tools and building materials.
○ Granite - build statues, fortresses, bridges, and public
buildings.
○ Basalt - cobblestones and as a material in
landscaping and roads.
○ Pumice - good abrasive for cleaning and polishing.
○ Obsidian - make sharp tools for cutting and scraping.
Lesson 2.4 - Sedimentary Rocks
How Do Sedimentary Rocks Form?
● Sediment is small, solid pieces of material
that come from rocks or living things.
● Sedimentary rocks form when sediment is
deposited by water and wind.
● Most sedimentary rocks are formed through a sequence of
processes: weathering, erosion, deposition, compaction,
and cementation.
The Three Major Types of Sedimentary Rocks
● clastic rock is a sedimentary rock formed when rock
fragments are squeezed together. (ex. shale, sandstone,
conglomerate)
● Organic rock forms where the
remains of plants and animals
are deposited in layers. (ex.
coal and limestone)
● Chemical rock forms when
minerals dissolved in a water
solution crystallize. (ex.
limestone and rock salt)
How Are Sedimentary Rocks Used?
● People have used sedimentary rocks for
many different purposes, including for tools
and building materials.
○ Flint used to make spearheads and
arrowheads.
○ Sandstone and limestone are used as
building materials. Limestone is used to
make cement and steel.
What Are Metamorphic Rocks?
● Any rock that forms from another rock as a
result of changes in heat or pressure (or both
heat and pressure)
● It can change both its shape and its
composition.
How Metamorphic Rocks Form?
● Pockets of magma can rise
through the crust. The high
temperatures of these pockets
can change rock
● Collisions between Earth’s plates can also
push rock down toward the heat of the mantle.
● Plate collisions cause great pressure to be
applied to rock while mountains are being
formed.
How Metamorphic Rocks are Classified?
● according to the arrangement of the
grains
○ either in parallel layers or bands are
said to be foliated. (most common)
○ Nonfoliated grains are randomly
arranged (ex. marble)
How Metamorphic Rocks Are Used?
● marble and slate are important materials
for buildings and sculptures.
● Ground up marble is also a component
of toothpaste, plastics, and paper
● Graphite, the “lead” in pencils, is a
mineral commonly found in
metamorphic rocks.
What Is the Rock Cycle?
● a series of processes that occur on
Earth’s surface and in the crust and
mantle that slowly change rocks
from one kind to another.
● Forces produce a slow cycle that
builds, destroys, and changes the
rocks in the crust.
● The changes of the rock cycle are
closely related to plate tectonics.
○ help drive the rock cycle by helping
to form magma, the source of
igneous rocks.
○ The collision of continental plates
can be strong enough to push up a
mountain range resulting in
sedimentary rock