Rocks & Minerals
Minerals
Saddle-shaped pink
dolomite crystals.
What is a Mineral?
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Naturally Occurring
Inorganic
Solid
Definite Chemical Formula
Definite Crystal Structure
Galena
Beryl
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?
- What about the ice in
your refrigerator?
Inorganic
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Formed by inorganic processes; not living
Does not contain chains of carbon atoms
Solid
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Not gas or liquid
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H2O as ice in a glacier or a snowflake is a
mineral, but liquid water in the ocean is not.
The element mercury is a metal that’s a liquid
at room temperature/pressure. Liquid
mercury is NOT a mineral!
Definite Crystal Structure

Highly ordered atomic arrangement of
atoms in regular geometric patterns
Pyrite
Fluorite
K-spar
Fluorite
Kyanite 8
Tourmaline
Crystal Structure of Ice
Definite Chemical Formula

Minerals are expressed by a specific
chemical formula
-Gold (Au)
-Calcite (CaCO3)
-Quartz (SiO2)
-Pyrite
(FeS2)
Composition of the Earth’s Crust
 Eight Elements that make up over 98%
of Earth’s Crust
-Oxygen (O)
-Silicon (SI)
-Aluminum (Al)
-Iron (Fe)
-Calcium (Ca)
-Sodium (Na)
-Potassium (K)
-Magnesium (Mg)
Where Do Minerals Come From?
Crystallize from magma and lava.
Olive crystallizes from
mafic magma.
Precipitate from water due to evaporation.
How Are Minerals Identified?
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Color
Luster
Hardness
Streak
Density
Crystal Shape
Cleavage and Fracture
Special Properties
Color

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
Luster

General appearance of a mineral surface in
reflected light
Glassy-Obsidian
Hardness
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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
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
Streak
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The color of a finely powdered mineral
Determined by rubbing the mineral on a piece
of unglazed porcelain (streak plate)
Density
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The amount of matter in a given space
(Mass/Volume)
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
One direction of cleavage
= basal cleavage (biotite
mica).
Octahedral Cleavage
forms bi-pyramids
(Fluorite)
Rhombohedral cleavage forms
“smushed” cubes (calcite).
Cleavage and Fracture
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Fracture occurs when a mineral breaks at
random lines instead of at consistent
cleavage planes.
Conchoidal fracture is what gives quartz,
obsidian, chert, and flint those supersharp edges!
Quartz has no cleavage and instead exhibits conchoidal fracture.
Special Properties
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Magnetism (Magnetite)
Optical Properties (calcite and ulexite)
Glowing under ultraviolet light (Fluorite)
Salty taste (Halite)
Smell (Sulfur)
Magnetite
Reaction to weak acids (Calcite)
Economic Importance of Minerals
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Minerals are in many things we see and
use everyday such as; bricks, glass,
cement, plaster, iron, gold
Every American Requires 40,000
Pounds of New Minerals per Year
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at this level of consumption the average newborn infant
will need a lifetime supply of:
-795 lbs of lead (car batteries, electric components)
-757 lbs of zinc (to make brass, rubber, paints)
-1500lbs of copper (electrical motors, wirings
-3593 lbs aluminum (soda cans, aircraft)
-32,700 lbs of iron (kitchen utensils, automobiles,
buildings)
-28,213 lbs of salt (cooking, detergents)
-1,238,101 lbs of stone, sand, gravel, cement (roads,
homes, etc.)
Rocks
Rocks
 Made of two or more different minerals
that have been:
 cemented together
 squeezed and heated together
 melted and cooled together.
Types of Rocks
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Igneous
Sedimentary
Metamorphic
Igneous Rocks
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Most igneous rocks are produced deep
underground by the cooling and hardening
of magma
Sedimentary Rocks
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Formed from the breaking apart of other
rocks (igneous, metamorphic, or
sedimentary rocks) and the cementation,
compaction and recrystallization of these
broken pieces of rock
Fact about the Mississippi River
Did You Know?
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The Mississippi River carries an average of
436,000 tons of sediment each day
It moves an average of 159,000,000 tons
of sediment a year
Metamorphic Rocks
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Formed from heat and pressure changing
the original or parent rock into a
completely new rock. The parent rock can
be either sedimentary, igneous, or even
another metamorphic rock.
The Rock Cycle
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The diagram of the rock cycle shows how the
earth's rocks are changed again and again
Classification of Igneous Rocks
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Composition-refers to the minerals that
make up the rock
Texture-shape, size, arrangement and
distribution of minerals that make up the
rock
Composition
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Extrusive- Formed from lava; volcanic
Obsidian
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Pumice
Intrusive- Formed deep within the earth
Granite
Textures
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Glassy
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Obsidian
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Fine-grained
Basalt
Coarse-grained
Granite
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Porphyritic
Granite
Classification of Sedimentary
Rocks
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Clastic Rocks- Made of the fragments of
previously existing rocks
Organic Rocks- Come from organisms
Chemical Rocks- Formed by inorganic
processes such as evaporation
Clastics Rocks
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Conglomerate
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Sandstone
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Mudstone
Organic Rocks
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Limestone
Coquina
Fossiliferous Limestone
Chemical Rocks
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Limestone
Metamorphic Rocks
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Foliated- Parallel alignment of flattened
mineral grains and pebbles
Unfoliated-Rocks that are not banded
and do not break into layers
Foliated
Gneisse
Unfoliated
Marble
Distribution of Rocks in the U.S.