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Rocks and Minerals
Part 1: Minerals
What Is A Mineral?
To be classified as mineral, a substance must:
1. Be a solid
2. Be formed naturally
3. Be inorganic (not from living things)
4. Have a crystal structure
5. Have a fixed chemical composition
Examples
Mineral… or not?
Mineral
NOT!
Not a solid.
Examples
Mineral… or not?
Mineral
NOT!
Not formed naturally.
Examples
Mineral… or not?
Mineral
NOT!
Not inorganic.
Examples
Mineral… or not?
Mineral
NOT!
Not inorganic.
Examples
Mineral… or not?
NOT!
NoNot
crystal
inorganic.
structure.
Mineral
Examples
Mineral… or not?
NOT!
No fixed composition.
Mineral
Review
To be classified as mineral, a substance must:
1. Be a solid
2. Be formed naturally
3. Be inorganic (not from living things)
4. Have a crystal structure
5. Have a fixed chemical composition
A Huge Variety…
Identifying Minerals
Minerals are identified using
7 key characteristics:
Color
Crystal Shape
Luster
Cleavage / Fracture
Streak
Special Properties
Hardness
1. Color
Color is an easy property to judge.
The problem with color is that it can
only be used to identify minerals with
their own unique and specific color.
For example, all the minerals shown are quartz!
2. Luster
Luster is how the mineral reflects light.
The 2 basic types of luster are:
Metallic
Non-Metallic
Non-metallic can be further divided into:
Silky, greasy, waxy, earthy, dull
3. Streak
Streak is the color of its powder.
It is found by rubbing the mineral on a
piece of porcelain called a streak plate
This causes tiny pieces of the mineral to
rub off, which reflects its true color
4. Hardness
Hardness is how hard it is to scratch a mineral.
Hardness in measured using
Moh’s Hardness Scale (1872).
Harder minerals (diamond) scratch softer
minerals (talc) and receive a higher rating.
Moh’s Hardness Scale
Hardest
Softest
10. Diamond
09. Corunudum
08. Topaz
07. Quartz
06. Orthoclase
05. Apatite
04. Fluorite
03. Calcite
02. Gypsum
01. Talc
5.5 Glass
4.5 Iron Nail
3.5 Penny
2.5 Fingernail
5. Crystal Shape
Crystals form in certain geometric shapes
which can be used to identify them.
Cubic
Trigonal
Tetragonal
Monoclinic
Hexagonal
Triclinic
Galena
(cubic)
Diamond
(trigonal)
Quartz
(tetragonal)
Wulfenite
(monoclinic)
Garnet
(hexagonal)
Axinite
(triclinic)
6. Cleavage or Fracture
When struck, minerals split in certain ways.
Cleavage is when a
mineral splits easily
along flat surfaces
Fracture is when a
mineral breaks apart in
an irregular way
Cleavage vs. Fracture
Calcite
(cleavage)
Quartz
(fracture)
7. Special Properties
Some minerals have their own unique properties.
Sulfur smells like rotten eggs.
Magnetite is naturally magnetic.
Halite tastes salty (because it’s salt!)
Review
Minerals are identified using
7 key characteristics:
Color
Crystal Shape
Luster
Cleavage / Fracture
Streak
Special Properties
Hardness
Common Minerals
Calcite
Barite
Common Minerals
Fluorite
Gypsum
Gem Minerals
Tourmaline
Opal
Gem Minerals
Beryl
(Aquamarine)
Diamond
Metallic Minerals
Pyrite
(on Sphalerite)
Gold
Metallic Minerals
Malachite
(copper ore)
Malachite
(cross section)
Colorful Minerals
Azurite
Vanadinite
Colorful Minerals
Tourmaline
Cavansite
Any Questions?
Rocks and Minerals
Part 2: Rocks
Types of Rocks
There are three major types of rocks:
Igneous
Metamorphic
Sedimentary
Igneous Rocks
Igneous comes from the Latin word for “fire”.
Igneous rocks form from the cooling
of molten rock called magma or lava.
Igneous rocks fall under 2 broad categories:
Intrusive Rocks
Extrusive Rocks
Rocks formed
beneath the Earth.
Rocks formed at the
Earth’s surface.
Intrusive Igneous Rocks
Intrusive igneous rocks form below the Earth’s
surface as magma cools and hardens.
Intrusive Igneous Rocks
Intrusive rocks have large crystals.
It is warm below the Earth.
Hot magma cools down slowly.
Minerals have lots of time
to combine together.
This forms coarse-grained
rocks with large crystals.
Granite
Extrusive Igneous Rocks
Extrusive igneous rocks form above the
Earth’s surface as lava cools and hardens.
Extrusive Igneous Rocks
Extrusive rocks have small crystals.
It is cooler at the surface.
Hot lava cools down quickly.
Minerals do not have a lot
of time to come together.
Basalt
This forms fine-grained
rocks with small crystals.
Extrusive Igneous Rocks
Some extrusive rocks are formed in mid-air!
Frothy lava is shot into the air
and cools down rapidly,
trapping gas bubbles inside it.
Scoria
Scoria & pumice are examples.
Both are full of tiny holes
and are very light!
Pumice
Extrusive Igneous Rocks
Scoria and pumice are formed here.
Extrusive Igneous Rocks
One extrusive rock is formed near water.
Water is cold.
Hot lava cools instantaneously.
There is NO time for minerals
to combine together.
This forms glassy rocks
with no crystals.
Obsidian
Extrusive Igneous Rocks
Obsidian is formed here.
Sedimentary Rocks
Sedimentary rocks are formed from sediments.
Sediments are small pieces of material
that come from rocks or living things.
There are 6 kinds of sediments:
shells
gravel
cobbles
sand
pebbles
silt or clay
Types of Sediments
Largest
shells
cobbles
pebbles
gravel
sand
Smallest
silt / clay
Formation of Sedimentary Rock
Sedimentary rocks are formed
through a series of processes.
1. Erosion
Running water,
wind or ice loosen
and carry away
sediments.
Formation of Sedimentary Rock
Sedimentary rocks are formed
through a series of processes.
2.1.Deposition
Erosion
The
sediments
settle
Running
water,
out or
of the
wind
ice water
loosen
or
wind
carrying
and
carry
away
it and
form layers.
sediments
.
Formation of Sedimentary Rock
Sedimentary rocks are formed
through a series of processes.
3.1.
Compaction
2.
Deposition
Erosion
Over
time, water,
layers
The
sediments
settle
Running
build
on
top,
out
of the
wind
orwater
ice
the
orpressing
wind carrying
loosen and carry
it and formtogether
layers. .
sediments
away sediments.
Formation of Sedimentary Rock
Sedimentary rocks are formed
through a series of processes.
4.1.
Cementation
3.
2.
Compaction
Deposition
Erosion
The
sediments
settle
During
Over
time,
compaction,
layers
Running
water,
out
of the
minerals
build
on
crystallize
top,
wind
orwater
ice
orpressing
windtogether
carrying
and
bind
the
to
loosen
and
carry
form
rock.
it and
form
layers..
sediments
together
away sediments.
Sedimentary Rock
Sedimentary rocks differ by particle size.
Shale is made from clay and
silt grains that settle on the
bottom of a river and are
cemented together.
Sandstone is made when
larger sand grains are
cemented together.
Sedimentary Rock
Sedimentary rocks differ by particle size.
Conglomerate is made from
rounded pebbles cemented
between grains of sand
and gravel.
Breccia is made from
angular cobbles cemented
between clay and sand
grains.
Sedimentary Rock
Sedimentary rocks differ by particle size.
Limestone is made from
shells of marine organisms
that have been crushed and
cemented together.
Coal is made from swamp
plants buried in water
and compressed over
millions of years.
Review
Largest
shells
limestone
cobbles
breccia
pebbles
sand
conglomerat
e
conglomerat
e
sandstone
silt / clay
shale
gravel
Smallest
Metamorphic Rock
Metamorph means to “change form”.
Metamorphic rocks are made when other rocks
are changed by heat and pressure in the Earth.
This causes the rock to change in:
appearance
texture
crystal
structure
mineral content
Two Categories
There are 2 main types of metamorphic rock.
Foliated
Non-foliated
Foliated rocks have
minerals arranged in
layers or bands.
Non-foliated rocks
have minerals
arranged randomly.
slate, gneiss
marble, quartzite
Metamorphic Rock
Metamorphic rock comes from existing rocks.
Shale
becomes Slate
Sandstone
becomes Quartz
Metamorphic Rock
Metamorphic rock comes from existing rocks.
Granite
becomes Gneiss
Limestone
becomes Marble
Any Questions?
Rocks and Minerals
Part 3: The Rock Cycle
The Rock Cycle
Rocks are destroyed and reformed continuously.
The rock cycle is a series of processes on Earth
that change rocks from one form to another.
Some of the changes are fast,
like in a volcanic eruption.
Some of the changes are slow,
like weathering and erosion.
Melting
Liquid
Magma
Metamorphic
Rock
Heat & Pressure
Sedimentary
Rock
Cooling
Igneous
Rock
Deposition
Compaction
Cementation
Weathering
Loose
Sediments
Any Questions?