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Powerpoint Presentation Physical Geology, 10/e


Title: Powerpoint Presentation Physical Geology, 10/e Author: steve kadel Last modified by: itlocal Created Date: 1/12/2004 8:59:44 PM Document presentation format – PowerPoint PPT presentation

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Title: Powerpoint Presentation Physical Geology, 10/e

  • A mineral is a naturally occurring, inorganic,
    usually non-biologic, crystalline solid, which is
    physically and chemically distinctive.
  • Form in the geosphere (most minerals),
    hydrosphere (e.g., halite, gypsum), biosphere
    (e.g., calcite, aragonite), and even the
    atmosphere (e.g., water ice, as snow)
  • Consistent and recognizable physical and chemical

Atoms and Elements
  • An element is a substance that can not be broken
    down into others by ordinary chemical reactions
  • An atom is the smallest unit of a substance that
    retains the properties of that element
  • Composed of 3 types of subatomic
  • particles
  • Protons (positively charged)
  • Neutrons (zero net charge)
  • Electrons (negatively charged)
  • A molecule is the smallest unit of a compound
    that retains the properties of that substance
    CaCO3, FeS2, CaSO4, SiO2, K(Mg, Fe)3AlSi3O10(F,

Atomic Structure
  • Protons and neutrons form the nucleus of an atom
  • Represents tiny fraction of the volume at the
    center of an atom, but nearly all of the mass
  • Electrons orbit the nucleus in discrete shells or
    energy levels
  • Shells represent nearly all of the volume of an
    atom, but only a tiny fraction of the mass
  • Numbers of electrons and protons are equal in a
    neutral atom
  • Ordinary chemical reactions involve only
    outermost shell (valence) electrons

  • Atoms of an element with different numbers of
    neutrons are called isotopes
  • Isotopes may be either stable or unstable
  • Stable isotopes retain all of their protons and
    neutrons through time, (e.g. Carbon-12,
    Carbon-13). These can be used to track natural
  • Unstable or radioactive isotopes spontaneously
    lose subatomic particles from their nuclei over
    time, (e.g. Carbon-14, U-238). These are sources
    of radiation and heat within the Earth, and can
    be used to date rocks and fossils.

Isotopes of Hydrogen
Stable isotopes of oxygen in water (ice) and
shells can be used to track climate change over
Chemical Bonding
  • Chemical bonding is controlled by outermost shell
    (valence) electrons
  • Elements will typically be reactive unless their
    valence shell is full
  • Atoms or groups of atoms with unequal numbers of
    protons and electrons, thus having a non-zero
    charge, are called ions
  • Positive and negative ions are attracted to one
    another and may stick or chemically bond together

Chemical Bonding
  • Ionic bonding
  • Involves transfer of valence electrons from one
    atom to another
  • Covalent bonding
  • Involves sharing of valence electrons among
    adjacent atoms
  • Metallic bonding
  • Electrons flow freely throughout metals results
    in high electrical conductivity

Ionic bonding of NaCl (sodium chloride)
The CNO Cycle
  • In the high temperature condition in the core
    of the high-mass stars, another fusion process
    (the CNO cycle) can fuses hydrogen into helium at
    a much faster rate than the proton-proton cycle.
  • The heavier elements (carbon, nitrogen, and
    oxygen) act as catalysis to speed up the hydrogen
    fusion process
  • The net result is the same as the proton-proton
    chain the creation of a helium atom and release
    of energy from fusion of four hydrogen nuclei
  • The numbers of carbon, nitrogen, and oxygen
    remain the same before and after the reaction.

Fusion Reactions in Stars to Make Heavy Elements
  • Fusion of carbon into heavier elements requires
    very high temperature, around 600 million
    degrees. There are many fusion reactions
    happening in the core of the stars. These
    reactions are responsible for producing the heavy
    elements. The simplest form is helium capture by
    heavier elements. Fusion between heavy elements
    are also possible.
  • Helium Capture
  • capture of helium by heavier elements such as
    Carbon, Oxygen, Neon, etc
  • Heavy element fusion
  • And a whole lot more reactions

Hydrogen and Helium abundance reflect physics of
Big Bang
Preference for even numbers b/c of He fusion
Elements heavier than Iron rare formed in nova
and supernova
Relative abundance of Elements in the Universe
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Composition of Earths Crust
  • Common elements
  • Nearly 98 of the atoms in Earths crust are
    represented by the 8 most common elements
  • O, Si, Al, Fe, Ca, Na, K, Mg
  • Common mineral types
  • Most minerals are silicates (contain Si and O
    bonded together)
  • Minerals have crystalline structures
  • Regular 3-D arrangement of atoms

Silicate Structures
  • The Silicon-Oxygen tetrahedron
  • Strongly bonded silicate ion
  • Basic structure for silicate minerals
  • Sharing of O atoms in tetrahedra
  • The more shared O atoms per tetrahedron, the more
    complex the silicate structure
  • Isolated tetrahedra (none shared)
  • Chain silicates (2 shared)
  • Double-chain silicates (alternating 2 and 3
  • Sheet silicates (3 shared)
  • Framework silicates (4 shared)

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Augite (inosilicate)
Tremolite (amphibole)
Biotite (mica)
Feldsapr (albite)
Non-silicate Minerals
  • Carbonates
  • Contain CO3 in their structures (e.g., calcite -
  • Sulfates
  • Contain SO4 in their structures (e.g., gypsum -
    CaSO4. 2H2O)
  • Sulfides
  • Contain S (but no O) in their structures (e.g.,
    pyrite - FeS2)
  • Oxides
  • Contain O, but not bonded to Si, C or S (e.g.,
    hematite - Fe2O3)
  • Native elements
  • Composed entirely of one element (e.g., diamond -
    C gold - Au)

  • A mineral must meet the following criteria
  • Crystalline solid
  • Atoms are arranged in a consistent and orderly
    geometric pattern
  • Forms through natural geological processes
  • Has a specific chemical composition
  • May include some internal compositional
    such as the solid solution of Ca and Na in
  • Rock-forming minerals
  • Although over 4000 minerals have been identified,
    only a few hundred are common enough to be
    generally important to geology (rock-forming
  • Over 90 of Earths crust is composed of minerals
    from only 5 groups (feldspars, pyroxenes,
    amphiboles, micas, quartz)

  • Ore minerals
  • Minerals of commercial value
  • Most are non-silicates (primary source of metals)
  • Examples magnetite and hematite (iron),
    chalcopyrite (copper), galena (lead), sphalerite
  • Must be able to be extracted profitably to be
    considered current resources
  • Gemstones
  • Prized for their beauty
  • and (often) hardness
  • May be commercially useful
  • Diamond, corundum, garnet, and
  • quartz are used as abrasives

Mineral Properties
  • Physical and chemical properties of minerals
    are closely
  • linked to their atomic structures and
  • Color
  • Visible hue of a mineral
  • Streak
  • Color left behind when mineral is scraped on
    unglazed porcelain
  • Luster
  • Manner in which light reflects off surface of a
  • Hardness
  • Scratch-resistance
  • Crystal form
  • External geometric form

Mineral Properties
  • Cleavage
  • Breakage along flat planes
  • Fracture
  • Irregular breakage
  • Specific gravity
  • Density relative to that of water
  • Magnetism
  • Attracted to magnet
  • Chemical reaction
  • Calcite fizzes in dilute HCl

Crystal Habit appearance in hand specimens
Massive, Granular, Compact find
grained Lamellar, Micaceous, Bladed layered Fibro
us, Acicular, Radiating needlelike Dendritic
branching Banded, Concentric, Geodes bands Botryo
idal, Globular, Stalactitic orbs etc. Oölitic,
Pisolitic pea like
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