Principles of Geology

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Principles of Geology

• Chapter 3
• Minerals

Mian Liu 2007
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Minerals the building blocks of rocks
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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
• Rock
• A solid aggregate of minerals

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Composition of minerals

• Elements
• Basic building blocks of minerals
• Over 100 are known (92 naturally occurring)

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Composition of minerals

• Atoms
• Smallest particles of matter
• Retains all the characteristics of an element

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The composition of minerals

• Atomic structure
• Nucleus
• Protons
• Neutrons
• Electrons
• Energy levels valence electrons

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Composition 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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Atomic structure
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The composition of minerals

• Bonding
• Ionic bonding
• Covalence bonding
• Other bonds

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Chemical bonding

• Atoms combines to form chemical compounds
• Ionic bond one or more valence electrons are
  transforms from one atom to another
• Covalence bond valence electrons are shared by
  atoms

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Halite (NaCl) An example of ionic bonding
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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 sharing of valence electrons
Form the molecule of chlorine gas (Cl2)
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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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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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Composition 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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Diamond and graphite polymorphs of carbon
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Relative abundance of the most common elements in
the continental crust
O 46.6 wt Si 27.7 Al 8.1 Fe 5.0 Ca 3.6 Na 2
.8 K 2.6 Mg 2.1 All others 1.7 Total 100
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Some of the Silicates minerals
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Mineral groups

• Important nonsilicate minerals
• Carbonates
• Primary constituents in limestone and dolostone
• Calcite (CaCO3) and Dolomite CaMg(CO3)2 are the
  two most important carbonate minerals

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Mineral groups

• Important nonsilicate minerals
• Many nonsilicate minerals have economic value
• Examples
• Hematite (oxide mined for iron ore)
• Halite (halide mined for salt)
• Sphalerite (sulfide mined for zinc ore)
• Native copper (native element mined for copper)

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Native copper
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Physical properties of minerals

• Crystal form
• Color
• Luster
• Streak
• Hardness
• Cleavage