Chapter 3 Matter and Minerals

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Chapter 3 Matter and Minerals
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Minerals Building Blocks of Rocks

• By definition a mineral is
• Naturally occurring
• Inorganic solid
• Ordered internal molecular structure
• Definite chemical composition
• A naturally occurring inorganic solid with a
  ordered internal molecular structure and a
  definite chemical structure.

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Pyrite and Quartz
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Pyrite Cubic
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Why Study Minerals

• Sources of resources to build consumer goods.
• Improves the quality of life.
• Nevada second largest producer of Gold
• In addition Nevada produces Silver, Copper, Lead,
  Zinc, Platinum, Arsenic, Barite

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Rocks

• By definition a rock is an aggregate of minerals.
• Granites consists of Quartz, Plagioclase, and
  Mica minerals

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Granite has Three Minerals
Potassium Feldspar
Quartz
Biotite
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Composition of Minerals

• Elements
• Basic building blocks of minerals
• Over 100 are known (92 naturally occurring).
• Compounds
• Minerals can consists of one elements such as
  Carbon (C), Diamonds, Gold (Au) Gold, HOWEVER,
  when two or more elements make up a mineral, that
  mineral is a COMPOUND.
• Example Sodium Na combines with Cl to form NaCl
  Halite.

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Atoms

• Atoms
• Smallest particles of matter.
• Retains the characteristics of an atom.

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Composition of Minerals

• Atomic structure
• Central region called the nucleus
• Consists of protons ( charges) and neutrons (no
  charge)
• Electrons
• Negatively charged particles that surround the
  nucleus
• Located in discrete energy levels called shells

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Structure of an Atom
Figure 3.4 A
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Composition of Minerals

• Chemical bonding
• Formation of a compound by combining two or more
  elements
• Ionic bonding
• Atoms gain or lose outermost (valence) electrons
  to form ions
• Ionic compounds consist of an orderly arrangement
  of oppositely charged ions

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Halite (NaCl) An Example of Ionic Bonding
Figure 3.6
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Composition of Minerals

• Covalent bonding
• Atoms share electrons to achieve electrical
  neutrality
• Generally stronger than ionic bonds
• Both ionic and covalent bonds typically occur in
  the same compound

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Covalent Bonding
Figure 3.7
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Composition of Minerals

• Other types of bonding
• Metallic bonding
• Valence electrons are free to migrate among atoms
• Weaker and less common than other bonds

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Structure of Minerals

• Minerals consist of an orderly array of atoms
  chemically bonded to form a particular
  crystalline structure
• Internal atomic arrangement in ionic compounds is
  determined by ionic size

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Geometric Packing of Various Ions
Figure 3.8
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Structure of Minerals

• Polymorphs
• Minerals with the same composition but different
  crystalline structures
• Examples include diamond and graphite
• Phase change one polymorph changing into
  another

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Diamond and Graphite Polymorphs of Carbon
Figure 3.10
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Physical Properties of Minerals

• Primary diagnostic properties
• Determined by observation or performing a simple
  test
• Several physical properties are used to identify
  hand samples of minerals

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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 3.11 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
Galena Also Has Cleavage
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Physical Properties of Minerals

• Color
• Often what we see first
• Often highly variable due to slight changes in
  mineral chemistryl.
• Exotic colorations of certain minerals produce
  gemstones.

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Quartz (SiO2) Exhibits A Variety Of Colors
Figure 3.26
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Physical Properties of Minerals

• Streak
• Color of a mineral in its powdered form on a
  tile.
• Hardness
• Resistance of a mineral to abrasion or
  scratching, glass, finger nail, penny.
• 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 3.12
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Mohss Scale of Hardness
Figure 3.13
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Physical Properties of Minerals

• Cleavage
• Tendency to break along planes of weak bonding
• Produces flat, shiny surfaces
• (Important)
• Described by resulting geometric shapes
• Number of planes
• Angles between adjacent planes

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Common cleavage directions
Figure 3.15
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Fluorite, Halite, and Calcite All Exhibit Perfect
Cleavage
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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 2.7

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Conchoidal Fracture
Figure 3.16
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Special and Specific Physical Properties of
Minerals

• Other properties
• Magnetism Magnetite
• Reaction to hydrochloric acid Calcite
• Reaction to hydrochloric acid when powered
  Dolomite
• Salt Taste Halite and Rock Salt
• Smell Sulfur Fire Works
• Elasticity Biotite and Muscovite Basal
• Marks on paper Graphite

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Mineral Groups

• Nearly 4000 minerals have been named.
• Rocks are an aggregate of minerals
• 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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Elemental Abundances in Continental Crust
Figure 3.18
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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 OLIVINE
Figure 3.19
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Mineral Groups

• Joining silicate structures
• Single tetrahedra are linked together to form
  various structures including
• Isolated tetrahedra
• Ring structures
• Single and double chain structures
• Sheet or layered structures
• Complex 3-dimensional structures

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Three Types of Silicate StructuresAugite
Hornblende Micas
Figure 3.21
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Mineral Groups

• Common silicate minerals
• Light silicates Feldspar group
• Most common mineral group
• Exhibit two directions of perfect cleavage at 90
  degrees
• Orthoclase (potassium feldspar) and Plagioclase
  (sodium and calcium feldspar) are the two most
  common members

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Potassium FeldsparThree-Dimensional Networks
Figure 3.24
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Plagioclase Feldspar Striations
Figure 3.25
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Mineral Groups

• Common silicate minerals
• Light silicates Quartz
• Only common silicate composed entirely of oxygen
  and silicon
• Hard and resistant to weathering
• Conchoidal fracture
• Often forms hexagonal crystals

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Mineral Groups

• Common silicate minerals
• Light silicates Muscovite
• Common member of the mica family
• Excellent cleavage in one direction
• Produces the glimmering brilliance often seen
  in beach sand

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Mineral Groups

• Common silicate minerals
• Light silicates Clay minerals
• Clay is a general term used to describe a variety
  of complex minerals
• Clay minerals all have a sheet or layered
  structure
• Most originate as products of chemical weathering

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Mineral Groups

• Common silicate minerals
• Dark silicates Olivine group
• High temperature Fe-Mg silicates
• Individual tetrahedra linked together by iron and
  magnesium ions
• Forms small, rounded crystals with no cleavage

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Mineral Groups

• Common silicate minerals
• Dark silicates Pyroxene group
• Single chain structures involving iron and
  magnesium
• Two distinctive cleavages at nearly 90 degrees
• Augite is the most common mineral in the pyroxene
  group

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Mineral Groups

• Common silicate minerals
• Dark silicates Amphibole group
• Double chain structures involving a variety of
  ions
• Two perfect cleavages exhibiting angles of 124
  and 56 degrees
• Hornblende is the most common mineral in the
  amphibole group

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Hornblende Amphibole
Figure 3.27
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Cleavage Angles For Augite and Hornblende
Figure 3.28
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Mineral Groups

• Important nonsilicate minerals
• Typically divided into classes based on anions
• Comprise only 8 of Earths crust
• Often occur as constituents in sedimentary rocks

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Table 3.2
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Mineral Groups

• Carbonates
• Calcite (CaCO3) and dolomite CaMg(CO3)2 are the
  two most important carbonate minerals.
• Primary constituents in limestone and dolostone
  rocks.

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Halides

• Halides Minerals with Cl, F, Br
• Halite Sodium Chloride NaCl. AKA Salt
• Fluorite Calcium Fluoride CaF2

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Oxides O2-

• Contain Oxygen O2
• Magnetite Fe3O4
• Hematite Fe2O3
• Limonite Fe2O3 H2O

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Sulfides S

• Contain Sulfur S
• Galena PbS
• Pyrite FeS2
• Chalcopyrite CuFeS2

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Sulfates

• Minerals with SO42-
• Gypsum CaSO4H2O

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Native Elements

• Platinum Pt
• Gold Au
• Silver Ag
• Copper Cu
• Diamond C
• Graphite C
• Sulfur S

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Native Copper
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