Chapter 1 Minerals: Building Blocks of Rocks

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Chapter 1 Minerals Building Blocks of Rocks
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Minerals Building Blocks of Rocks

• By definition a mineral is/has
• Naturally occurring
• Inorganic solid
• Ordered internal molecular structure
• Definite chemical composition

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Rocks are an aggregate of minerals
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Composition and Structure of Minerals

• Atoms Elements Minerals Rocks

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Earth Composition
Earth Consists of the Core, Mantle, and Crust
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Elemental Abundances in Continental Crust
Figure 1.14
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Elemental Abundances Earth as a whole vs Crust
Earth
Crust

• Oxygen 35
• Iron 24
• Silicon 17
• Magnesium 14
• Sulfur 6
• Aluminum 1
• Calcium 1

• Oxygen 47
• Iron 5.5
• Silicon 27
• Magnesium 2.1
• Sulfur lt1
• Aluminum 8
• Calcium 3.7

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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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Structure of an Atom
Figure 1.5 A
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Structure of an Atom
Figure 1.5 A
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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

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Physical Properties of Minerals

• Crystal form
• External expression of a minerals internal
  structure
• Often interrupted due to competition for space
  and rapid loss of heat

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A Garnet Crystal
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Cubic Crystals of Pyrite
Figure 1.7 A
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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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Galena (PbS) Displays Metallic Luster
Figure 1.13
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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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Quartz (SiO2) Exhibits a Variety of Colors
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Physical Properties of Minerals

• Streak
• Color of a mineral in its powdered form
• 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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Streak Is Obtained on an Unglazed Porcelain Plate
Figure 1.8
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Mohs Scale of Hardness
Figure 1.9
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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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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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Conchoidal Fracture
Figure 1.12
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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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Mineral???????

• Quartz Yes No
• Coal Yes No
• Pearls Yes No
• Amethyst Yes No
• Shells Yes No
• Water Yes No
• Ice Yes No
• Iron Yes No

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Mineral Groups

• Nearly 4000 minerals have been named
• Rock-forming minerals
• Common minerals that make up most of the rocks of
  Earths crust
• Only a few dozen members
• Composed mainly of the 8 elements that make up
  over 98 of the continental crust

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Mineral Groups

• Silicates
• Most important mineral group
• Comprise most rock-forming minerals
• Very abundant due to large of silicon and
  oxygen in Earths crust
• Silicon-oxygen tetrahedron
• Fundamental building block
• Four oxygen ions surrounding a much smaller
  silicon ion

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Two Illustrations of the SiO Tetrahedron
Figure 1.15
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Mineral Groups

• Common silicate minerals
• Feldspar group
• Most common mineral group
• Quartz
• Only common silicate composed entirely of oxygen
  and silicon

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Potassium Feldspar
Figure 1.17
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Mineral Groups

• Important nonsilicate minerals
• Comprise only 8 of Earths crust
• Often occur as constituents in sedimentary rocks

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Table 1.1
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Mineral Groups

• Important nonsilicate minerals
• Carbonates
• Primary constituents in limestone and marble
• Limestone is used commercially for road paving,
  building stone, and as the main ingredient in
  Portland cement

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Mineral Groups

• Important nonsilicate minerals
• Halite and gypsum
• Both are commonly found in thick layers
• Like limestone, both halite and gypsum are
  important nonmetallic resources

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Mineral Groups

• Important nonsilicate minerals
• A number of other minerals have economic value
• Examples
• Hematite (oxide mined for iron ore)
• Sphalerite (sulfide mined for zinc ore)
• Galena (lead)
• Native copper (native element mined for copper)

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Native Copper
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Mineral Resources and Reserves

• Resources are minerals that can be recovered for
  use
• Reserves include mineral deposits already
  identified that can be profitability extracted
• Resources include reserves, deposits that can not
  economically recovered, and minerals not yet
  discovered

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Florida Production

• 4th in states for non fuel minerals
• Top 3 in the states for crushed stone, cement,
  and peat
• 1st in states in heavy mineral sales
• 1st in world for phosphate production

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Florida Production - Phosphate

• 90 used for fertilizer
• 5 for livestock feed supplement
• 5 used in food products, chemicals and ceramics

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Florida Production Crushed Stone

• Limestone and coquina
• Used for construction
• Limestone used for cement

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Florida Production Clays

• Used for absorbents, anti-acids, and whiteners

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Florida Production Heavy Minerals

• Found in Sands
• Main minerals include ilmenite and rutile both
  metamorphic minerals
• Used as paint pigments, paper, and plastics

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End of Chapter 1