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EARTH’S STRUCTURE
Chapter 2: Minerals and Rocks
2.1 Properties of Minerals
What is a Mineral?
• Mineral: a naturally occurring solid that can form
by inorganic processes and that has a crystal
structure and a definite chemical composition.
• Let’s break this down ---
What is a Mineral?
• Mineral: a naturally occurring solid that can
form by inorganic processes and that has a
crystal structure and a definite chemical
composition.
• This means that minerals
are formed by natural
processes in and on Earth.
What is a Mineral?
• Mineral: a naturally occurring solid that can form
by inorganic processes and that has a crystal
structure and a definite chemical composition.
• This means that minerals are all solid, with a
definite volume and shape.
• The particles are packed together tightly.
What is a Mineral?
What is a Mineral?
• Mineral: a naturally occurring solid that can form
by inorganic processes and that has a crystal
structure and a definite chemical composition.
• This means that minerals are formed from items
that were not a part of a living organism.
What is a Mineral?
• Mineral: a naturally occurring solid that can form
by inorganic processes and that has a crystal
structure and a definite chemical composition.
• A crystal is a repeating pattern of flat sides
(faces) that meet at sharp edges and corners.
What is a Mineral?
What is a Mineral?
• Mineral: a naturally occurring solid that can form
by inorganic processes and that has a crystal
structure and a definite chemical composition.
• A mineral always contains the exact chemical
structure – the same elements are present in the
same proportions.
What is a Mineral?
Minerals, Compounds, & Elements
• Almost all minerals are compounds.
• Compound: two or more elements that are combined
so that the elements no longer have their own
properties.
• Each mineral has a unique combination of
elements.
• Some elements, like copper, silver, and gold, are also
minerals.
Identifying Minerals
• Color:
• Many minerals share the same color
• Not a great way to identify the minerals
Identifying Minerals
• Streak:
• Color of the powder left behind from the mineral
• The streak is not always the same color as the mineral
Identifying Minerals
• Luster:
• How light is reflected from a mineral’s surface
• Metallic, glassy, earthy, silky, waxy, and pearly
Identifying Minerals
• Hardness:
• One of the most useful ways to identify minerals
• Mohs Hardness Scale ranks minerals from 1-10, with 10 being the
hardest (Diamond) and 1 being the softest (Talc).
• Determined by a scratch test – scratch unknown mineral by known
minerals to see if a scratch appears or not.
Identifying Minerals
• Density:
• Unique to each mineral
• Mass divided by volume
• Depends on how the atoms are arranged in the mineral
Identifying Minerals
• Crystal Structure:
• All crystals in a mineral have identical patterns
• Good to identify small samples
• Beams reflect light in specific patterns
Identifying Minerals
• Cleavage and Fracture:
• Cleavage: a mineral that splits easily along flat surfaces; depends
on how the crystals are arranged.
• Fracture: a mineral breaks apart in an irregular way
Identifying Minerals
• Special Properties:
• Magnetism
• Glow in UV light
• Bends light
• Conducts electricity
CHAPTER 2: MINERALS
AND ROCKS
2.2 Classifying Rocks
Classifying Rocks
• About 20 minerals make up most of the rocks on Earth’s
crust.
• These are called rock-forming minerals.
• A rock’s color gives clues to the minerals that make it up.
• Granite is usually light colored and rich in oxygen and silica, while
basalt is generally dark colored with a low silica content.
Classifying Rocks
Texture
• Grains give the rock its texture, the look or feel of a
rock’s surface.
• Grain size: rocks with large grains are coarse grained, rocks with
small grains are fine-grained rocks.
Texture
• Grains give the rock its texture, the look or feel of a
rock’s surface.
• Grain shape: rounded grains form a conglomerate rock, jagged
grains form breccia.
Texture
• Grains give the rock its texture, the look or feel of a
rock’s surface.
• Grain pattern: patterned layers of grains form a banded rock, while
rocks with no patterns are non-banded.
Rocks
• There are three main types of rocks:
• Igneous: forms from the cooling of magma/lava.
• Sedimentary: forms when small particles are pressed and
cemented together.
• Metamorphic: forms when an already existing rock is changed by
heat, pressure, or chemical reactions.
CHAPTER 2: MINERALS
AND ROCKS
2.3 Igneous Rocks
Igneous Rocks
• These rocks are classified by their:
• Origin
• Texture
• Mineral composition
Origin
• Igneous rocks can form below or above ground.
• If they are formed below ground, they are made of
magma and are said to be intrusive.
• Granite is the most abundant intrusive rock.
• If they are formed above ground, they are made of lava
and are said to be extrusive.
• Basalt is the most common extrusive rock.
Origin
Texture
• Texture depends on the size and shape of its
mineral crystals.
• Rapidly cooling lava forms fine-grained igneous
rocks with small crystals or no crystals. (extrusive)
• Slow cooling magma forms coarse-grained rocks
with large crystals. (intrusive)
Mineral Composition
• Lava low in silica usually forms dark rocks.
• Magma high in silica usually forms light rocks.
Uses for Igneous Rocks
• Because they are hard, dense, and durable, igneous
rocks are used for tools and building materials.
CHAPTER 2: MINERALS
AND ROCKS
2.4 Sedimentary Rocks
Sedimentary Rocks
• Sediment is small, solid pieces of material that come from
rocks or living things.
• Processes like weathering, erosion, deposition,
compaction, and cementation help form sedimentary
rocks.
Sedimentary Rocks
• Weathering: the breaking apart/wearing down of
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materials.
Erosion: the movement of sediment
Deposition: the depositing, or laying down, or sediment.
Compaction: the process that presses sediments
together.
Cementation: the process in which dissolved minerals
crystallize and glue sediments together.
Sedimentary Rocks
• There are three main groups of sedimentary rocks:
• Clastic rocks
• Organic rocks
• Chemical rocks
Clastic Rocks
• A sedimentary rock formed when rock fragments are
squeezed together.
• Grouped by the size of the rock fragments
• Examples: shale, sandstone, conglomerate, and breccia.
Organic Rocks
• Forms where the remains of plants and animals are
deposited in layers.
• Coal forms from swamp plant remains.
• Limestone forms in the ocean from animals with shells
made of calcite.
Chemical Rocks
• Forms when minerals dissolved in a water solution
crystallize.
• Sometimes these are formed from mineral deposits in
seas/lakes that evaporate.
• Such as halite (rock salt)
• Limestone is an example of this when calcite is dissolved
and crystallizes.
Uses for Sedimentary Rocks
• Again, many types of sedimentary rocks are used for tools
and building.
CHAPTER 2: MINERALS
AND ROCKS
2.5 Metamorphic Rocks
Metamorphic Rocks
• Any rock that forms from another rock as a result of
changes in heat or pressure or both is called
metamorphic.
Classifying Meta. Rocks
• Foliated Rocks:
• When grains are arranged in parallel layers or bands in the rock.
• Slate is an example; formed from shale.
Classifying Meta. Rocks
• Non-foliated Rocks:
• The grains in these rocks are arranged randomly.
• Quartzite forms from quartzite sandstone.
• Marble forms from limestone.
Using Meta. Rocks
• Marble is great for sculpting into different shapes, so it is
used in statues and buildings.
• Slate is also used in many building structures because it
splits into layers easily.
CHAPTER 2: MINERALS
AND ROCKS
2.6 The Rock Cycle
The Rock Cycle
• Series of processes that occur in and on Earth to slowly
change rocks from one kind to another.
• There is no set pathway for rocks to follow.
The Rock Cycle
• The changes that rocks go through are related to plate
tectonic activity.
• Plate movement helps to form and move magma,
mountains, and other structures.
• Materials are not lost during the change, they are just
transformed.
The Rock Cycle
The Rock Cycle