Rocks
and
Minerals
Minerals
the building blocks of rocks
Mineral Characteristics
• natural
• inorganic
• solid
• definite composition
• crystal structure
Mineral Formation
4 major processes by which minerals
form:
1. Crystallization from magmacooling magma causes minerals to
crystallize
2. Precipitation
• Minerals dissolve out
of evaporated water;
precipitated
3. Pressure and Temperature
Muscovite
Talc
• Change in pressure
and temperature
cause an existing
mineral to
recrystallize while
still solid
4. Hydrothermal
Solutions
• A hot mixtures of water
with substances dissolved
in them. When they come
in contact with existing
minerals- a chemical
reaction occurs forming a
new mineral
Bornite
Mineral Composition
Minerals are grouped or classified based on
their composition. There are 6 groups
1. Carbonates - contain
carbon, oxygen, and one ore
more metallic element
2. Silicates
- formed from silicon and
oxygen
- elements combined to
form a silicon
tetrahedron, 1 silicon
atom and 4 oxygen atoms
- formed from cooling
magma
- either near the surface
(few crystals) or deep
below surface (larger
crystals)
3. Oxides
- Minerals that
contain oxygen and
one or more other
element(s)
Gypsum
4. Sulfates and
Sulfides
- Minerals containing
sulfur
Pyrite
5. Halides
-minerals containing
halogen ions plus
one or more other
elements
Halite
6. Native Elements
Minerals that exist in a
relatively pure form
gold, silver, copper
Gold crystal structure
Mineral Properties
Mineral PROPERTIES
are used to identify
minerals based on
specific
characteristics
Luster
Streak
Color
Specific Gravity
Cleavage & Fracture
Hardness
Magnetism
Fluoresence
Streak
color of a mineral in
its powder form
Color
often not a good
property for Iding
Luster
how light is reflected from the
surface of a mineral
Cleavage- tendency to break along
flat, even surfaces (mica)
Fracture- uneven breakage (quartz)
Specific Gravity- ratio of a mineral’s
density to the density of water
Specific Gravity =
mass (g) of dry sample
mass lost in water
Specific Gravity is a ratio…so
Specific Gravity has no units
Hardness- measure of resistance of a
mineral being scratched
Magnetism
Fluorescence
Magnetite
Double Refraction
Calcite
Smell
Sulfur
Rocks and
The Rock
Cycle
Rocks- any solid mass of mineral
or mineral-like matter that occurs
naturally as part of our planet
• There are 3 major type or families or rock:
– Igneous rocks
– Sedimentary rocks
– Metamorphic rocks
Igneous Rocks
• Magma- molten material underground
• Lava- magma that reaches the surface
• Igneous rocks are formed from magma that
has cooled and hardened either beneath the
surface or from a volcanic eruption
2 Ways to Form Igneous Rock
• Intrusive Igneous
Rocks- form when
magma hardens
beneath Earth’s
surface
• Magma intrudes into
existing rocks
• Extrusive Igneous
Rocks- form when
lava hardens on the
surface of the Earth
• Extruded onto the
surface
rhyolite
granite
• Magma contains some gases, including
water vapor- this make it less dense, so it
rises
• As magma rises, it cools and forms crystals
• The longer the cooling time the larger the
crystals
Classification of Igneous Rocks
Igneous rocks are classified by texture
and composition
• Texture refers to the appearance of an
igneous rock (size, shape, arrangement of
crystals)
• Composition refers to the proportions of
light and dark minerals in the rock
• Coarse- grained Texture- form as a result
of slow cooling, ions can move = large
crystal size
• Fine-grained Texture- form as a result of
quick cooling time, ions lose motion= small
crystal size
• Glassy Texture- form from lava that cools
rapidly, ions don’t have time to arrange =
glassy texture
• Porphyritic Texture- rocks with different
size minerals that form from varying
cooling rates
• Felsic Composition- contain
mainly quartz and feldspar,
some with biotite mica and
amphibole. Make up major
rocks of continental crust
• Mafic Composition- contain
mainly dark colored minerals
and feldspar, along with Mg
and Fe. Darker and denser than
granitic composition
Classification of Major Igneous Rocks
Texture is crossed with composition to classify igneous rocks. For
example, granite has a coarse texture due to slow cooling and larger
crystals, and a light color from the light colored quartz and feldspar
minerals used to form it.
Sedimentary Rocks- formed from
compacted and cemented sediments
• Weathering physically and chemically
breaks rocks into small pieces called
sediments
• Sediments are moved
by wind, water, ice,
and gravity
• Eventually, they are
dropped and form layers
that are cemented together
Weathering, Erosion, and
Deposition
• Weathering breaks
rocks down
• Erosion involves
weather and the
removal of rock
• Deposition is the
dropping of sediments
• Sediments are
deposited according to
size
Compaction and Cementation
• Compaction is the
process that squeezes
the water out of the
sediments. It is caused
by the weight of the
sediments.
• Cementation takes
place when dissolved
minerals are deposited
in the tiny spaces among
the sediments.
• Cementing holds the
sediments together.
Classification of Sedimentary Rocks
• Clastic Sedimentary
Rocks are formed
from weathered bits of
rocks and minerals
• Organic Sedimentary
Rocks are formed
from living materials
• Chemical
Sedimentary Rocks
are formed when
dissolved minerals
precipitate from water
solution
limestone
rock salt
• Sedimentary rocks hold many clues to the
Earth’s history
• Layers of sediments are records of geologic
events on Earth
• Fossils are unique to sedimentary rocks
Sedimentary rocks drop according
to size; larger particles fall first
followed by smaller particles
Metamorphic Rocks- form when
existing rocks undergo change through
heat and pressure
• Metamorphism means
to change
• Most metamorphic
changes occur at high
temperatures and
pressure
• These occur deep
below the Earth’s
surface and extend
into the mantle
Forms of Metamorphism
• Contact
Metamorphismforms when magma
intrudes into existing
rock
• Changes in rocks are
minor
• Regional
Metamorphismformed during
mountain building
process that occur
over a large area
• Major changes to
rocks
Contact metamorphism
Regional metamorphism
Agents of Metamorphism
• Heat- causes existing
minerals to
recrystallize or new
minerals to form
• Pressure- causes the
spaces between
mineral grains to
close= more compact
rock= greater density
Classification of Metamorphic
Rocks- based on texture and composition
• Foliated
Metamorphic Rocksform when minerals
recrystallize at right
angles to the direction
of force
• Causes a layered or
banded appearance
• Nonfoliated
Metamorphic Rocksno banded texture
• Most contain only one
mineral
Foliated
NonFoliated
slate
marble
schist
gneiss
The Rock Cycle
The Rock Cycle
Thinking about relationships among
the major rock groups
Major Rock Groups
• Igneous
– Formed from a melt (molten rock)
– Plutonic (intrusive):slow cooling and crystallization
– Volcanic (extrusion): quick cooling at the surface
•Sedimentary
–Formed at the Earth’s surface
–Clastic (Mineral Fragments or grains, clays)
–Chemical (crystalline chemical/biochemical precipitates)
–Organic (made from living material: shells, plants)
•Metamorphic
–Changed by pressure, heat and fluids.
Fig. 2.9
MAGMA
IGNEOUS
Crystallization
MAGMA
46
IGNEOUS
Intrusive/Plutonic
Crystallization
MAGMA
47
Extrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
Crystallization
MAGMA
48
Weathering
Extrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
Crystallization
Uplift
MAGMA
49
Weathering
SEDIMENT
Extrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
Crystallization
Uplift
MAGMA
50
Weathering
SEDIMENT
Erosion
Transport
Deposition
Extrusive/Volcanic
SEDIMENTARY
IGNEOUS
Intrusive/Plutonic
Crystallization
Uplift
MAGMA
51
Weathering
SEDIMENT
Erosion
Transport
Deposition
Extrusive/Volcanic
SEDIMENTARY
IGNEOUS
Intrusive/Plutonic
Crystallization
Uplift
MAGMA
52
Weathering
SEDIMENT
Erosion
Transport
Deposition
Extrusive/Volcanic
SEDIMENTARY
IGNEOUS
Intrusive/Plutonic
Increased P&T
METAMORPHIC
Crystallization
Burial
Uplift
MAGMA
53
Weathering
SEDIMENT
Erosion
Transport
Extrusive/Volcanic
Add the
IGNEOUS
Shortcuts
Deposition
SEDIMENTARY
Intrusive/Plutonic
Increased P&T
METAMORPHIC
Crystallization
Melting
Burial
Uplift
MAGMA
54
Weathering
SEDIMENT
Erosion
Transport
Deposition
Extrusive/Volcanic
SEDIMENTARY
IGNEOUS
Intrusive/Plutonic
Increased P&T
METAMORPHIC
Crystallization
Melting
Burial
Uplift
MAGMA
55
Weathering
SEDIMENT
Erosion
Transport
Deposition
Extrusive/Volcanic
SEDIMENTARY
IGNEOUS
Intrusive/Plutonic
Increased P&T
METAMORPHIC
Crystallization
Melting
Burial
Uplift
MAGMA
56
In Conclusion…
• The rock cycle demonstrates
the relationships among the
three major rock groups
• It is powered by the interior
heat of the Earth
• As well as earth’s
momentum and…
• The energy from the sun
• It involves processes on the
Earth’s surface as well as
the Earth’s interior
• It connects the “hydrologic
cycle” with the “tectonic
cycle”.
ROCK CYCLE
• The surface of the
Earth is made of rock
• ROCK is a collection
of one or more
minerals, mixed
together into a solid
substance
Rock Cycle
• The Series of processes in which rock forms
and changes from one type to another by
geological processes.
PROPERTIES OF ROCKS
• BOWEN’S
REACTION SERIES:
The pattern that shows
how minerals form
crystals when they
cool based on their
chemical make-up and
melting point
The Rock
Cycle
-Melting & Intrusion
-Solidification of melt
-Mountain Building
-Uplift & Exposure
-Weathering
-Erosion & Transport
-Deposition & Burial
-Metamorphism
-Melting & Intrusion
Fig 4.9
The Rock Cycle
Convergent Plate
Boundary
-Subducting slab
-Mantle melting
-Bouyant rise of melt
Fig 4.9
The Rock Cycle
Convergent Plate
Boundary
- Solidification of melt
- Volcanic activity
Extrusive
rocks
Intrusive
rocks
Fig 4.9