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Transcript
Minerals
Chapter 3
Naturally Occurring



Minerals must occur
naturally.
Cannot be man made.
Cement, bricks, steel,
and glass all come
from materials found
in the earth, but these
are made by people.
Inorganic


Inorganic materials
were never living.
Coal is made from
the remains of
ancient plants and
animals, so coal is
not a mineral.
Minerals




Naturally occurring
Inorganic solid
Crystal structure
Definite chemical
composition
Solid



The state of matter
when the material is
below its freezing
point.
Definite shape,
definite volume.
Particles are fixed in
place.
Crystal Structure


The particles of the
material line up in a
regular, repeating
pattern.
Has flat sides called
faces, that meet at
sharp edges and
corners.
Definite Chemical Composition



Always contains certain
elements in the same
proportion.
Almost all minerals are
compounds, which are two
or more different elements
bonded together (holding
hands).
Pyrite is two sulfur atoms
holding hands with an
atom of iron.
Chemical Formula’s




Have a definite format.
Written together means
they are bonded.
Coefficients tell how
many of the whole thing
you have.
Subscripts tell how many
of the atom before it that
you have.



So 2H means two
separate hydrogen
atoms.
H2 mean two hydrogen
atoms holding hands.
H2O means two
hydrogen atoms
holding hands with an
oxygen atom.
More Formula’s


2 H2O means you
have two separate
water molecules, each
containing two
hydrogen and one
oxygen atom.
Bornite is a copper ore
that turns purple when
exposed to air. It’s
formula is Cu5FeS4.




So how many of each
atom are present?
Five copper
one iron
four sulfur
Identifying Minerals

Each mineral has
specific properties that
can be used to identify
it.

Hardness
density
luster
color
streak
crystal system
cleavage and fracture
special properties







Hardness



A measure of how
easily a mineral can
be scratched.
Determined by the
atomic structure of the
mineral.
Friedrich Mohs
developed the scale
we use today.
Density


Minerals will have a
certain density
regardless of the size
of the sample.
When geologists
compare the weight of
the mineral to the
weight of an equal
volume of water it is
called specific gravity.
Color

Not especially useful
in identifying minerals,
as some minerals like
quartz can come in a
variety of colors.
Luster




The way a mineral
reflects light.
Can be metallic or
non-metallic.
Shiny or dull.
Earthy, waxy, pearly,
glassy.
Streak



The color of its
powder.
Not always the same
as the color of the
mineral.
Pyrite has a gold
color, but its streak is
a greenish black.
Gemstones

Gemstones are highly
valued for their beauty
and rarity, than for their
usefulness.

Important gemstones
include diamond,
sapphire, ruby, emerald,
aquamarine, topaz, and
tourmaline.
Rocks
Chapter 4
Rocks are:


A solid made of one or
more minerals and
other materials.
A solid that makes up
the crust of a planet.
Classifying Rocks

Rocks are classified based on how they were
formed.
Identifying Rocks




Rocks are further identified by:
color
texture
mineral composition
Chapter 4
Section 1 The Rock Cycle
Types of Rock
Click below to watch the Visual Concept.
Visual Concept
Texture

Texture is the quality of a rock that is based on the
sizes, shapes, and positions of the rock’s grains.
Composition


Composition is the chemical makeup of a rock.
Composition can describe either the minerals or other
materials in the rock.
Grains


Particles of minerals
that make up a rock.
Texture is determined
by grain size, grain
shape, and grain
pattern.
Grain Size




Some rocks have
grains that are large
and easy to see.
These rocks are
coarse grained.
Other rocks have
grains so small they
are microscopic.
These are fine grained
rocks.
Grain Shape




Grains can be:
fine sand
crystals
fragments that can be
smooth or jagged
Grain Pattern




Grains can lie flat in
layers like a stack of
pancakes.
Some have patterns
that look like waves or
swirls
Some resemble rows
of beads.
Others will have
random patterns.
No Visible Grain



Some rocks resemble
pieces of glass.
These rocks cooled
very quickly so
crystals did not have
time to grow.
This is obsidian, a
volcanic glassy
extrusive rock.
Mineral Composition

Since rocks are really
combinations of
minerals, geologists
must slice their
samples into very thin
pieces to test which
minerals are present.
Origin of Rocks




Rocks are classified by
the way they are formed.
Igneous rocks: formed
from the cooling of
molten rock.
Sedimentary rocks:
formed from sediments
being compacted and
cemented.
Metamorphic rocks:
existing rock that is
changed by heat,
pressure, or chemical
reactions.
Igneous Rocks





Identified by
origin, texture,
and mineral
composition.
From the Latin
word “ignis,”
which means fire.
Tend to have
average densities.
Form from the
cooling of
molten rock.
Also called
plutonic rock.
Extrusive Igneous Rock


Extrusive rock is
formed from lava that
erupted on the surface
and rapidly cooled.
Will have tiny crystals,
be very fine grained,
and sometimes even
appear glassy.
Basalt is most
common of this type.
Basalt Forming
Intrusive Igneous Rock



Forms when magma
cools underground.
Usually cools slowly,
so it will have large
crystals and be coarse
grained.
Granite is most
common intrusive
rock.
Large Crystals


Lava at the surface
cools quickly, so
crystals do not have
time to grow.
Rock is a good
insulator, so rock
cooling underground
takes much longer.
So intrusive rock will
have larger crystals.
Explain This!


How would you
explain an intrusive
rock that had both
large and small
crystals?
Right! It must have
cooled slowly at first,
then cooled more
rapidly as it got closer
to the surface.
Porphyritic Rock


These rocks look like
Jell-O with fruit
mixed in.
Deep underground
the heat cannot
dissipate as rapidly,
so the rock cools
slowly. Near the
surface the heat can
escape into the air,
so it cools rapidly.
Felsic Igneous Rock


Lighter colored
igneous rocks will
have lots of silica.
They tend to be
less dense than
the darker
versions.
Mafic Igneous Rock


Less silica means
these rocks will be
darker than their felsic
counterpart.
They will be denser
also.
Little silica →→→→→→→→→→→→ lots of silica
The Formation
of the Earth.


When the earth was
formed 4.6 billion
years ago, it was
molten all the way to
the core.
So when the crust
cooled, the first
rocks were igneous.
All other rock would
come from this.
Sill


Slab of volcanic rock
that squeezes
between rock layers.
Tend to be horizontal.
Dike


Slab of volcanic rock that
cuts across rock layers.
Tend to be vertical.
Batholith



A very large mass of
volcanic rock that form
deep underground.
Can cover several states
in the USA.
Stone Mountain might be
part of an exposed
batholith.
Stock


Smaller area of volcanic rock than a
batholith
Stone Mountain might be a stock that is
exposed.
Sedimentary Rocks

Formed from particles
of sediment deposited
by wind and water
being compacted and
cemented.

Sediment is small
pieces of solid
materials that come
from rocks or living
things.
Origins of Sedimentary Rock

Wind, water, ice, sunlight,
and gravity all cause rock
to physically weather into
fragments.

Through erosion, these
rock and mineral
fragments, called
sediment, are moved
from one place to another.

The sediment is
deposited in layers, and
eventually newer layers
cover the older layers.
Chapter 4
Section 3 Sedimentary Rock
Sedimentary Rock Cycle
Click below to watch the Visual Concept.
Visual Concept
Question?

What do these rocks
have in common?
Stratification


Yes, all these rocks
are layered or
“stratified.”
Strata is Latin for
layer.
Forming Sedimentary Rock
Weathering

The process by which
exposed rock is
broken down into
small pieces by the
elements of nature
(wind, rain, ice,
chemical actions,
plants, etc.)
Erosion

Occurs when water or
wind loosens rock and
soil and carries it
away.
Deposition


The process by which
the sediment settles
out of the water or air
carrying it.
Sediment is deposited
when the wind or
water slows down.
Compaction



As the sediments settle they will loosely fit on top of
each other.
As the years go by, more and more sediment is
added.
The bottom layers get compacted by the weight of
the layers above them.
Cementation



While compaction is
going on, minerals in
the rock slowly
dissolve.
The dissolved minerals
seep into the spaces
between the compacted
sediment.
They crystallize and
glue the sediments
together.
Lithification






The process by which
sediment becomes
sedimentary rock.
From Greek word “lithos,”
which means rock.
Erosion
Deposition
Compaction
Cementation
Types of Sedimentary Rocks



Clastic: formed when
rock fragments are
squeezed together.
Organic: (biological)
formed from the
remains of living
things.
Chemical: formed
when dissolved
minerals crystallize.
Clastic Sedimentary Rock
Shale



Clastic rock formed
from tiny particles of
clay.
Water deposits tiny
clay particles in thin
layers.
Feels smooth and
splits easily into flat
sheets.
Sandstone



Formed from sand on
beaches, ocean floors,
river beds, and
deserts.
Mainly quartz.
Lots of small holes
between the grains, so
it will absorb water.
Conglomerate and Breccia



Formed from a mixture
of rock fragments of
different sizes.
Conglomerate has
rounded edges.
Breccia has larger
fragments with sharp
or jagged edges.
Breccia
Organic Sedimentary Rocks


Formed from the
remains of plants and
animals that were
deposited in thick
layers.
Also called biological
rock.
Coal




Formed from the
remains of ancient
swamps.
As layer upon layer of
dead plants built up,
the bottom layers were
compacted into coal.
Stored chemical
energy from the sun.
Fossil fuel.
Coal Pictures
Limestone



Formed from the
shells of ancient sea
animals and plants.
Shells fall to the
bottom of the ocean in
layers, some 100’s of
meters thick.
Compaction creates
limestone.
Chalk



Formed from the
shells of ancient sea
life.
Creates layers 100’s
of feet thick
White Cliffs of Dover
Chalk Cliffs
Chemical Sedimentary Rocks


Formed when water
with dissolved
minerals evaporates.
The left behind
minerals will
crystallize.
Gypsum


Made from calcium
deposits.
Used to make sheet
rock for homes.
Halite



Rock salt
Formed from seas and
oceans that dried up.
The salt forms large
crystals.
Metamorphic Rocks



“Meta” is ancient
Greek for change.
“Morphosis” is ancient
Greek for form.
Metamorphic rock
then is rock that has
changed from one
form to another by
heat and pressure..
Origins of Metamorphic Rock

Metamorphic rocks are rocks
in which the structure, texture,
or composition of the rock
have changed. All three types
of rock can be changed by
heat, pressure, or a
combination of both.

A rock’s texture or mineral
composition can change
when its surroundings
change. If the temperature or
pressure of the new
environment is different from
the one in which the rock
formed, the rock will undergo
metamorphism.
Contact Metamorphism

Contact Metamorphism When
magma moves through the
crust, the magma heats the
surrounding rock and changes
it.

Some minerals in the
surrounding rock are changed
into other minerals by this
increase in temperature.

The greatest change occurs
where magma comes into direct
contact with the surrounding
rock.
Regional Metamorphism

Regional metamorphism
occurs when pressure
builds up in rock that is
buried deep below other
rock formations, or when
large pieces of the Earth’s
crust collide with each
other.

The increased pressure
and temperature causes
rock to become deformed
and chemically changed.
Section 4 Metamorphic Rock
How Metamorphic Rocks Form



Deep below the Earth’s
surface the intense heat
and pressure can change
rocks.
Their appearance, texture,
crystal structure and
mineral content can
change.
Fossils will be destroyed.
Almost melted!


Metamorphic rocks are
often squished, smeared
out, and folded.
Despite these
uncomfortable conditions,
metamorphic rocks do not
get hot enough to melt, or
they would become
igneous rocks!
Deformation


Change in a rock
caused by forces
placed on it.
Rock can be bent,
squeezed,
stretched or
folded.
Classifying Metamorphic Rock




Classified by the
arrangement of the
grains.
Foliated
Non-foliated
Usually harder and
denser than the rock
they come from.
Texture of Metamorphic Rock



All metamorphic rock
has one of two
textures.
Foliated
Metamorphic Rock
Non-foliated
Metamorphic Rock
gneiss
quartzite
Foliated Metamorphic Rock




Grains are in
parallel layers or
bands.
“Foliated” is the
Latin word for leaf.
Describes the thin
layering found in
many metamorphic
rocks.
These rocks will
split along these
bands.
Slate



Formed when shale is
subjected to pressure.
Denser, more
compacted than shale.
Produces flat plates
when broken.
Slate to Schist

If slate is subjected to
even greater pressure
and moderate
temperatures, schist is
formed.
Granite to Gneiss


Granite becomes
gneiss when subjected
to heat and pressure.
The atoms end up
lining up in bands.
Non-foliated Metamorphic Rock




Mineral grains are
randomized.
Amorphous
Do not split into layers.
Usually smoother and
denser than the parent
rock.
Quartzite


Occurs when
sandstone is
compressed by
pressure.
Usually very hard.
Marble


Formed from
metamorphosed
limestone.
Much harder and
denser.
Foliated Metamorphic
The Rock Cycle