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Minerals
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Minerals
Chapter 1
Minerals are the alphabet of geology
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Common Uses of Minerals
In groups of three
List as many uses of minerals as you can think of
Any group with more than 20 items gets to
“pass”
pass” next time I call on them.
• If you’
you’re not sure if something is a legitimate use,
include it.
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Minerals: Building Blocks of Rocks
By definition a mineral is/has
•
•
•
Naturally occurring
Inorganic solid
Ordered internal molecular structure
Atoms arranged in crystalline structure
• Definite chemical composition
Chemistry varies within a fixed range
Rock
• A solid aggregate of minerals
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In this bag I have a mineral
What is one thing you can tell me about what I
have in this bag?
Solid
Naturally
occurring
Inorganic
Has a definite
chemical
structure
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Are these things Minerals?
Piece of dried skin
Piece of window glass
A piece of naturally occurring glass (obsidian)
Lump of coal
Silly putty
Water
Ice
A rock
Piece of quartz
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Composition and Structure of Minerals
Elements
• Basic building blocks of minerals
• Over 100 are known (92 naturally occurring)
Atoms
• Smallest particles of matter
• Retain all the characteristics of an element
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Composition and Structure of Minerals
Atomic structure
• Central region called the nucleus
Consists of protons (+ charges) and neutrons (charges)
• Electrons
Negatively charged particles that surround the
nucleus
Located in discrete energy levels called shells
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The structure of atoms
Read about this or recall from other classes
Protons, neutrons, electrons
Atomic number
Bonds
Ions
Isotopes
Figure 1.3
An “Element” is a substance
made of one type of atom.
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Composition and Structure of Minerals
Chemical bonding
• Formation of a compound by combining two or
more elements
• Atoms gain or lose outermost electrons to form
ions
• Oppositely charged ions attract one another to
produce a neutral chemical compound
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Composition and Structure of Minerals
Isotopes and radioactive decay
• Mass number = sum of neutrons + protons in an
atom
• Isotope = atom that exhibits variation in its mass
number
• Unstable isotopes emit particles and energy in a
process known as radioactive decay
Atoms Bond Together to Make Molecules
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Share electrons
“Ions”
Ions” are atoms with too many or too few electrons
“-” or “+” charged
The charge of molecules is neutral
Na lacks an electron
• “+” charge
Cl has an extra electron
• “-” charge
They share ☺
Figure 1.4
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Common elements in Earth’
Earth’s crust
Element
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%wt
Oxygen
O 46.6
Si 27.7
Al 8.1
5.
Fe
Ca 3.6
Na 2.8
2.6
K
Mg 2.1
Silicon
Aluminum
Iron
Calcium
Sodium
Potassium
Magnesium
All Other Elements
In this bag I have
a mineral.
Guess what the 2
main elements in
my mineral are.
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Oh, say Al, Fred could not kiss Meg.
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Silicate Minerals
Most,
Most, but not all,
all, rockrock-forming minerals contain
silicon and oxygen.
“Silicate Minerals”
Minerals”
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Take 6 Toothpicks…
Toothpicks…
Form 4 equal triangles without crossing, bending,
or breaking any toothpicks.
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SiliconSilicon-Oxygen Tetrahedron
Each Oxygen
has a charge
of –2.
Each Silicon
has a charge
of +4
What is the
charge of the
tetrahedron?
Figure 1.10
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Identifying Minerals
Read about this – Especially if you are taking the
lab!
Crystal form
Luster
Color
Streak
Hardness
Cleavage
Fracture
Specific gravity (density)
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Silica Tetrahedra
Balance Charge in 2 Ways
Attaching to metals
Which usually have + charges
+
+
Fe 2 Fe 2
Sharing Oxygen atoms
Reducing charge on each tetrahedron
Or Both
Fe
Mg
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Common Silicate Minerals Form by
By Combing Silica Tetrahedra and/or
Attaching Metals
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Single Tetrahedron
Olivine
Combines with
Iron and/or
Magnesium
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Single Chains of Tetrahedra
Group: Pyroxene
Example: Augite
Combines with
Iron and/or
Magnesium
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Double Chains of Silica Tetrahedra
Group: Amphibole
Example: Hornblende
Combines with
Iron and/or
Magnesium
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Sheets of Silica Tetrahedra
Groups: Mica
Examples:
Biotite
Muscovite
Combines with
Iron and/or Magnesium: Biotite
(Black Mica)
Aluminum and/or Potassium:
Muscovite (White Mica)
ThreeThree-dimensional Networks of
Tetrahedra
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Feldspar (“
(“Field Rock”
Rock”)
Orthoclase (Potassium(Potassium-rich)
Plagioclase (Calcium & SodiumSodium-rich)
Figure 1.12
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ThreeThree-dimensional Networks of
Tetrahedra
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Quartz
Just Silicon and
Oxygen
All Oxygen atoms
are shared
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Identifying Minerals
Crystal Form
Cleavage
Breaks in a Regular Pattern
Luster
Metalic,
Metalic, glassy, earthy (dull), pearly
Color
Streak
Color of powdered mineral
Hardness
Fracture
Breaks in an Irregular Pattern
Specific Gravity
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Physical Properties
of Minerals
Crystal form
• External expression of a mineral’
mineral’s internal
structure
• Often interrupted due to competition for space
and rapid loss of heat
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Crystal Form
Sometimes visible in
large crystals
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Physical Properties
of Minerals
Cleavage
• Tendency to break along planes of weak bonding
• Produces flat, shiny surfaces
• Described by resulting geometric shapes
Number of planes
Angles between adjacent planes
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Fluorite, Halite, and Calcite All Exhibit
Perfect Cleavage
Figure 1.11
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Cleavage – How it Breaks
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1 Cleavage Plane
3 Cleavage Planes
No Cleavage Planes –
“amorphous”
amorphous”
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Physical Properties
of Minerals
Luster
• Appearance of a mineral in reflected light
• Two basic categories
Metallic
Nonmetallic
• Other descriptive terms include vitreous, silky,
or earthy
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Luster
Metallic
Dull
Glassy
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Physical Properties
of Minerals
Color
• Generally unreliable for mineral identification
• Often highly variable due to slight changes in
mineral chemistry
• Exotic colorations of certain minerals produce
gemstones
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Color and Streak
Beware of using color to identify some minerals
Trace amounts of impurities can change color
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Streak
Streak
Color of mark when scratch rock on
abrasive plate
Color of a mineral in its powdered form
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Streak Is Obtained on an Unglazed
Porcelain Plate
Figure 1.8
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Physical Properties
of Minerals
Hardness
• Resistance of a mineral to abrasion or scratching
• All minerals are compared to a standard scale
called the Mohs scale of hardness
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Hardness
Determine by what the mineral can scratch
Mohs Hardness Scale
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Talc
Cypsum
Calcite
Flourite
Apatite
Potassium Feldspar
Quartz
Topaz
Corundum
Diamond
2.5 Fingernail
3.5 Penny
5.5 Glass, Knife
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Mohs Scale
of
Hardness
Figure 1.9
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Physical Properties
of Minerals
Fracture
• Absence of cleavage when a mineral is broken
Specific Gravity
• Weight of a mineral/weight of an equal volume of
water
• Average value = 2.5 – 3.0
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Physical Properties
of Minerals
Other properties
•
•
•
•
•
•
•
Magnetism
Reaction to hydrochloric acid
Malleability
Double refraction
Taste
Smell
Elasticity
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Discuss the following questions in pairs.
Explain different ways in which silica tetrahedra
join together.
The mineral pictured below can be split into thin
sheets. What accounts for this?
Sort these minerals from simplest silicate
structure to most complex.
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Quartz
Pyroxene
Amphibole
Olivine
Feldspar
Mica
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About Minerals
> 2000 different minerals have been
identified
About 100 are “Common”
Common”
About 20 are very common and can be
identified by most geologists and geology
students.
A few of these are nonnon-silicate
Don’
Don’t contain silicon – oxygen tetrahedra
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NonNon-silicate Minerals
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Most metal ores
Oxides
• Iron oxide, Aluminum oxide, Zinc oxide
Sulfides
• Iron, lead, zinc, copper
Sulfates
Building materials
• Gypsum, Barite
Halides
Salt (NaCl
(NaCl)) = Halite
Carbonates
Calcite, Dolomite
Native Elements
Gold, Silver, Copper, Graphite
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Oxides
Hematite
IronIron-oxide
minerals.net/mineral/sulfates/gypsum/gypsum.htm
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Sulfides
Calcopyrite
Fools gold
CopperCopper-Iron Sulfide
Used as Copper Ore
Pyrite
Fools gold
Iron Pyrite
Cubic
Cleavage
Once used as source of sulfur
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Sulfates
Gypsum
Calcium Sulfate
Used in building materials
• Wallboard, cement
minerals.net/mineral/sulfates/gypsum/gypsum.htm
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Halides
Halite
Rock salt
Sodium Chloride
Used
• In Foods
• For DeDe-icing
minerals.net/mineral/sulfates/gypsum/gypsum.htm
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Carbonates (CO3)
Calcite
Calcium Carbonate
Used in
•
•
•
•
•
Building materials
Medicines
Fertilizers
Paint
…
minerals.net/mineral/sulfates/gypsum/gypsum.htm
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Native Elements
Gold
Used for
jewelry,
sculpture,
electric circuits
Silver
minerals.net/mineral/sulfates/gypsum/gypsum.htm
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Who Wants To Be A Geologist?
From a group of volunteers I will randomly select
a contestant.
The contestant will have the opportunity to
impress his or her peers and win candy.
The contestant can only keep the candy if he or
she correctly answers at least 4 questions.
The contestant has 4 life lines:
3 - Ask the audience
1 - 50/50
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Which of the following is NOT a
mineral?
A.
C.
Quartz
Coal
B.
D.
Ice
Diamond
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Which of the following statements about
minerals is true?
A.
They are harder
than the average
fingernail
C.
They are
transparent
B.
They have a
crystalline structure
D.
They contain
siliconsilicon-oxygen
tetrahedra
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What are the most common elements in
Earth’
Earth’s crust?
A.
Oxygen, Silicon,
B.
Oxygen, Silicon,
Aluminum, Iron,
Aluminum, Fluorine,
Carbon, Nitrogen,
Carbon, Nitrogen,
Potassium, Manganese
Krypton, Magnesium
C.
Oxygen, Silicon,
D.
Oxygen, Silicon,
Aluminum, Iron,
Aluminum, Iron,
Calcium, Nitrogen,
Calcium, Sodium,
Potassium,
Potassium, Magnesium
Magnesium
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What is the green mineral in the picture
below?
A.
C.
Green quartz
Emerald
B.
D.
Olivine
Jade
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Atoms are composed of what subatomic
particles?
A.
Ions, Isotopes and
Neurons
C.
Protons, Neutrons
and Electrons
B.
Protons, Neurons
and Electrons
D.
Protons, Neutrons
and Ions
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Reading and Homework
Read Chapter 2 in Lutgens
Homework
Lutgens Online
• Chapter 2 Assessment
Multiple Choice, and
Identification
Due 28 February 2007, at 5:00 PM
E-mail results to me at [email protected]
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