Rocks & Minerals
Minerals
What is a Mineral?
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is a natural, nonliving solid with a definite
chemical structure
A mineral is a substance that must fit all
parts of the definition
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Natural
Nonliving solid
Definite chemical structure
Are made up of crystals
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Partials of crystals are arranged in a particular,
repeating pattern
Naturally Occurring
Formed by natural processes not in the
laboratory
- Is an Ice Cube a mineral?
- Is the ice on the windshield of a car a
mineral?
- Is copper a mineral?
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How Are Minerals Identified?
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Color
Luster
Hardness
Streak
Density
Crystal Shape
Cleavage and Fracture
Special Properties
Color
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Usually the first and most easily observed
-Some minerals are always the same color
-Some minerals can have many colors
ROSE QUARTZ
QUARTZ
SMOKY QUARTZ
Properties of Minerals
 Luster
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This is a gem stone called
tourmaline it has a glassy
luster
The way a mineral
reflects light.
Can be metallic or
non-metallic.
Shiny or dull.
waxy, pearly, glassy.
Hardness

Resistance to scratching by different
items; “scratchability”
Mohs Hardness Scale
>2 fingernail
3 penny
~5 Steel of a pocket knife
5.5 Window Glass
6.6 Steel of a file
7 quartz crystal
Properties of Minerals
 Streak
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http://geology.csupomona.edu/alert/mineral/streak.htm
The color of its
powder.
Not always the same
as the color of the
mineral.
The mark it makes
when rubbed against
an unglazed tile
Properties of Minerals
 Density
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http://www.astronomynotes.com/cosmolgy/
Minerals will have a
certain density
regardless of the size
of the sample.
Each mineral has its
own density called
specific gravity
Crystal Shape
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Minerals have a characteristic crystal
shape resulting from the atomic packing of
the atoms when the mineral is forming
Cleavage and Fracture
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Cleavage is the tendency of a mineral
to split or crack along parallel or flat
planes
Fracture occurs when a mineral breaks
at random lines instead of at consistent
cleavage planes.
BIOTITE
1 Direction of Cleavage
QUARTZ
No Cleavage
Obsidian
Conchoidal Fracture
Mohs Mineral Hardness Scale
1) Talc
Softest
2) Gypsum
3) Calcite
1
5
4) Flourite
5) Apatite
9
2
6) Feldspar
6
7) Quartz
8) Topaz
3
7
9) Corundum
10) Diamond
10
Hardest
4
8
Rocks
Rocks classification
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http://geology.com/rock-tumbler/tumbling-rough.shtml
Texture
Grain
Minerals
Color
Origin of rocks
Rock classification
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ocal.wasp.uwa.edu.au/.../rock/rock16.jpeg
Texture is how a rock
looks and feels
texture in rocks is
determined by the
size, shape, and
pattern of a rocks
grains.
Rock Classification
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Grain
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http://www.union.edu/PUBLIC/GEODEPT/COURSES/geo-10/metamorphic.htm
Size -- large, small
Shape --smooth,
rough, round jagged
Pattern – rows, waves,
swirls, beads or
random patterns
Rock classification
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Mineral
composition
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blue.utb.edu/.../PHYS1417SPR00/Unit3Lec.html
Rocks are made of
more than one
mineral
Rock Classification
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Origin of
rocks
How were
the rocks
formed
- magma
- erosion and
layering
- heat and
pressure
Origin of rocks
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www.energyinst.org.uk/education/glossary/
Sedimentary
rocks are formed
from other rocks
that are broken into
small particles and
moved by erosion
(wind or water)
The particles are
squeezed or
cemented together
Rocks are layered
Origin of rocks
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Igneous rocks are
formed from the
cooling of magma or
lava
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www.outreach.canterbury.ac.nz/.../igneous.jpg
Lava is magma that
reaches the earth’s
surface
Origin of rocks
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Metamorphic rocks are formed from other
rocks
Rocks have been pushed deep into the earth’s
crust
Pressure from the earth above and heat from
the mantle below cause them to change shape,
color, grain and crystal structure
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0607/es06
07page01.cfm?chapter_no=visualization
Rock cycle
http://www.classzone.com/books/earth_science/terc/content/investigati
ons/es0602/es0602page02.cfm
Clues to the Past
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Rocks have clues to that tell us about past
events
Scientetist can look at rocks especially
sedimentary rocks because they form in
layers.
The oldest layers are on the bottom
Relative dating lets scientist place past
events in sequential order
Clues to the Past
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The Grand Canyon was formed 5 million years
ago when the Colorado River cut through the
sedimentary rocks. This provides a great deal of
information about Earth’s History
Fossils
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Fossils can form when an organism is buried in
soft mud
Most Fossils form from hard parts like bones,
shells, or wood.
Burrows and footprints can also be fossilized.
Many fossils were made by species that are now
extinct.
Fossils can help scientist determine the rock’s
age
Why is Soil important to living
things
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Weathering is when weather, water and
living things break down rocks and
create soil.
Weathering takes place over many years.
What makes up soil?
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Rock
Clay
Silt
Sand
Humus
3 Layers of Soil:
topsoil, subsoil and bedrock
What is topsoil?
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Topsoil is the upper surface of soil.
It is a natural product of subsoil and
bedrock.
Topsoil is the best for plant growth.
What is Subsoil and Bedrock?
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Subsoil and bedrock are layers of soil
under the topsoil that are formed over a
long period of time by water.
Subsoil and bedrock aren’t as good for
growing plants as topsoil
What is Humus?
(“HYOO-mus”)
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Humus is decayed or dead matter in soil.
It adds nutrients to the soil.
Humus is found in topsoil.
What is Clay?
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Clay contains small particles of soil that
hold water well and provides nutrients.
What is Sand?
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Sand is made up of small grains of worndown rock.
It has few nutrients.
Sand doesn’t hold water well
What is Silt?
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Silt is composed (made up of) very small
broken pieces of rock.
Its particles are larger than clay and
smaller than sand.