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Chapter 4
Characteristics of a Mineral:
• Naturally occurring
 Formed by natural processes
• Inorganic
 Not living – never will be
• Solid with specific chemical composition
 Definite shape & volume (NOT LIQUID OR GAS)
 Have a formula (chemical composition) unique to it
• Definite crystalline structure
 Atoms are arranged in a regular geometric pattern that is
repeated over and over again
1.
2.
3.
4.
Oxygen
Silicon
Aluminum
Iron
5.
6.
7.
8.
Calcium
Sodium
Magnesium
Potassium
Minerals are formed in three ways:
1.
Cooling Magma – Magma is molten (melted) material
found beneath the Earth’s surface. As it cools, it forms
crystals that then form minerals (the longer they cool, the
larger the crystals!)
2.
Water can only dissolve so much solid in a solution. Once
it reaches that point, all other solids precipitate (fall to
bottom). What precipitates are crystals – thus minerals.
3.
When elements DO dissolve in solution, if liquid
evaporates, solid crystals remain. Crystals = Minerals.
•Largest
group of rock-forming minerals.
•All Silicates contain Oxygen (O) and Silicon (Si)
•Si and O are the two MOST ABUNDANT elements in the
Earth’s crust and make up 96% of the Earth’s crust
•Examples include Feldspar and Quartz
•Contains
CO3 with metallic elements
•Some have distinctive coloration
•Examples include calcite and dolomite
•Found in limestone, coquina, and marble
•Compounds
of oxygen and a metal
•Examples include Hematite and Magnetite
•Source of iron and uranium
Ways to Identify Minerals:
• Color
 Trace elements will give off a specific color
• Luster
 The way a mineral reflects light
 Either metallic (shiny) or nonmetallic (dull)
• Texture
 How the mineral feels to the touch (smooth, rough, greasy,
soapy)
• Streak
 The color of a mineral when broken and powdered on a
porcelain streak plate
• Hardness
 How easily a mineral can be scratched
 “Rate” on Moh’s Hardness Scale, which ranges from 1-10
• Cleavage & Fracture
 Cleavage – when a mineral splits evenly along one or
more flat planes
 Fracture – when minerals break along rough or jagged
edges
• Density & Specific Gravity
 Differences in weight are due to differences in density
(mass per unit of volume)
 Reflects the atomic weight and structure, NOT THE SIZE
OR SHAPE
ORES
A mineral that contains a useful substance and can be mined for profit
Most ores are obtained through open-pit mining
Examples – Iron, Aluminum, Hematite, Aluminum, Rutile (contains titanium… sports
equipment!)
GEMS
Valuable minerals prized for their rarity and beauty
Examples – Ruby, Emeralds, Diamonds
IGNEOUS ROCKS
CHAPTER 5
What are Igneous Rocks?
•I G N E O U S R O C K S F O R M F R O M T H E C O O L I N G A N D
CRYSTALLIZATION OF MAGMA
•I G N E O U S I S L A T I N F O R “ F I R E ”
•M O S T I G N E O U S R O C K S A R E A S S O C I A T E D W I T H F I E R Y L A V A
FLOWS
•( L A V A I S S I M P L Y M A G M A T H A T F L O W S O N T O T H E S U R F A C E O F
THE EARTH).
Magma is formed from the
heat and pressure from
inside the Earth.
Magma is made up of
molten rock, gases, and
minerals.
The amount of silica
determines the melting
temperature and how
quickly magma flows.
How Igneous Rocks Melt and Form
Rocks melt in different ways, based on their composition
This explains why magma is a mixture of crystals and molten rock
Partial Melting
 The process where
some minerals melt at
low temperatures
while others remain
solid
 As the water content
of a rock increases, the
melting point
decreases
Fractional Crystallization
 The process where
different minerals
solidify at different
temperatures
Classifying Igneous Rocks
IGNEOUS ROCKS ARE CLASSIFIED
ACCORDING TO THREE MAIN THINGS:
1. MINERAL COMPOSITIONS
2. GRAIN SIZE
3. TEXTURE
Grain Size
Varies depending on the
amount of time lava/magma
takes to cool
Extrusive Igneous Rocks
Outside of Earth, lava cools
quickly and produces little to
no visible crystals (Fine)
Intrusive Igneous Rocks
Inside of Earth, magma cools
slowly and produces large
crystals (Coarse)
Texture
As grains crystallize
from magma, they grow
together and form
irregular edges.
Although this is
characteristic of many
igneous rocks, wellshaped crystals can also
form under certain
conditions.
Many rocks have
porphyritic texture,
which is characterized
by large, well-formed
crystals surrounded by
finer-grained crystals of
the same or different
material.
Chapter 6
SEDIMENTARY ROCKS
WHERE DO SEDIMENTARY ROCKS COME FROM?

Sedimentary Rocks come from sediments, which
are pieces of solid material deposited by wind,
water, ice, etc.

Sediments cover most of the Earth’s surface.

When sediments become cemented and compact
together, they form Sedimentary Rocks.

The formation of Sedimentary Rocks begins when
weathering and erosion produce sediments.
FORMATION OF SEDIMENTARY ROCKS
1.
Weathering: processes that break rock into smaller pieces


2.
Erosion: removal and movement of sediments



3.
Chemical Weathering – occurs when the minerals in a rock are
dissolved or otherwise chemically changed
Physical Weathering – rocks break into smaller grains (clastic
sediments) and remain chemically unchanged
By wind, water, gravity, glaciers
Deposition – when sediments are laid down (largest at bottom and
smallest at top)
Burial
Lithification: processes that transform sediments into rock


Compaction – weight of overlying sediments forces the sediment
grains closer together, causing physical changes
Cementation – occurs when mineral growth cements sediment grains
together into solid rock
FEATURES OF SEDIMENTARY ROCKS
The primary feature of sedimentary
rocks is bedding, or horizontal
layering.
Bedding can range in size,
dependent upon the method of
transport.
Fossils are the best known features
of sedimentary rocks.
Fossils show evidence of past life.
Sedimentary rocks, unlike other
rocks, can be used to determine the
type of animals that lived when the
rock was formed.
TYPES OF SEDIMENTARY ROCKS
There are three main types of sedimentary rocks:
1. Clastic Sedimentary Rocks



2.
Chemical Sedimentary Rocks


3.
Most common, resulting from lithification of clastic sediments
Formed from the abundant deposits of loose sediments found on
Earth’s surface
Classified according to their particle size
Form from evaporation – evaporites
Most commonly form in arid regions, in oceans and drainage
basins on continents with low water flow
Organic Sedimentary Rocks

Form from remains of living organisms
METAMORPHIC
ROCKS
Chapter 6
What are Metamorphic Rocks?
 The
word metamorphism is derived from the
Greek words “meta” (change) and “morphe”
(form)
 During metamorphism, a rock changes form
while remaining solid
 So, a metamorphic rock is one that is formed
when high temperature and pressure changes a
rock without melting it

A rock can change texture, mineralogy, or
chemical composition
How does a Rock undergo
Metamorphism?
 The
intense heat required for metamorphism
ultimately come from the Earth’s internal heat,
either through deep burial or nearby igneous
intrusions.
 The
high pressures required for metamorphism
can be generated in two ways:
1.
2.
From vertical pressure caused by the weight of
overlying rock
From the comprehensive forces generated as
rocks are deformed during mountain building
Two Types of Metamorphism
Regional Metamorphism
Contact Metamorphism
High temperatures and
pressures affect large
regions of Earth’s crust
Caused when molten
rock comes in contact
with solid rock
Metamorphic
Textures
Metamorphic Rocks are
classified into textured
groups.
Foliated – wavy layers
and bands of minerals
Nonfoliated – lack
mineral grains with long
axes in one direction