Volcanoes and Igneous Activity Earth Chapter 4

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MINERALS AND ROCK
Part 1 Minerals Chapter 2 11th Edition Part
2 Rock Chapter 3
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• Part 1
• Minerals

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Minerals the building blocks of rocks

• Definition and characteristics of a mineral
• Natural formed by geologic processes
• Inorganic
• Solid with the temperature ranges on earths
  surface
• Possess an orderly crystalline internal structure
  of atoms (see Figure 2.2)
• Have a definite chemical composition
• Made up of one, two or more elements, e.g.,
  quartz (SiO2) consists of two elements, while
  sulfur, gold and silver consist of only one
  element

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• Orderly arrangement of sodium and chloride ions
  in the
• Mineral halite

Fig. 2.2
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Mineral or Rock?

• Rocks are more loosely defined
• Any solid mass of mineral, or mineral-like,
  matter occurring naturally as part of the planet
• May be composed entirely of one mineral, e.g.,
  limestone consists of calcite
• Most consist of aggregates of several kinds of
  minerals, e.g., granite (Fig. 2.3)
• The properties of each mineral are retained

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Fig. 2.3
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Composition and structure of minerals

• Elements
• Basic building blocks of minerals
• Over 100 are known
• An element cannot be broken down into simpler
  substances by chemical or physical means
• Atoms
• Smallest particles of matter
• Have all the characteristics of an element

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Periodic table of the Elements
Figure 2.4
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How atoms are constructed

• Nucleus central part of an atom that contains
• Protons positive electrical charges
• Neutrons neutral electrical charges
• Energy levels, or shells
• Surround nucleus
• Contain electrons negative electrical charges
• Outermost shell contains the valence electrons

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Simplified view of the atom
Figure 2.5
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How atoms are constructed

• Atomic number is the number of protons in an
  atom's nucleus
• The mass number is the total of protons and
  neutrons
• Bonding of atoms
• Forms a compound with two or more elements
• Valence electrons responsible for bonding
• Ions are atoms that gain or lose electrons
• Isotopes
• Have varying number of neutrons

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Fig. 2.6
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How atoms are constructed

• Isotopes
• Have different mass numbers the sum of the
  neutrons plus protons
• Many isotopes are radioactive and emit energy and
  particles through a process known as radioactive
  decay
• Powers the movement of Earths crust and upper
  mantle
• Rate of decay is measurable used for dating

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Properties of minerals

• Primary physical properties of minerals
• Crystal form
• External expression of internal orderly
  arrangement
• Dependent on space restriction
• Less restriction more well-defined crystal faces
  
• Luster
• Appearance or quality of light reflected from the
  surface of mineral
• Metallic and non-metallic luster
• Color
• Could be unreliable due to impurities
• Streak
• Color of a mineral in its powdered form
• More reliable than color
• Obtained by rubbing against a streak plate
• Hardness
• One of the most useful diagnostic properties
• A measure of resistance to scratching or abrasion
  
• Determined by robbing a mineral against another
  object of known or assumed hardness
• Use of Mohs scale

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Properties of minerals

• Physical properties of minerals
• Fracture
• When the breakage is not along a defined plane
• Specific gravity
• Compares the weight to the weight of an equal
  volume of water
• Secondary or special properties (limited number
  of minerals)
• Taste
• Smell
• Elasticity
• Malleability

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Minerals

• Secondary or special properties of minerals
• Feel
• Magnetism
• Double Refraction
• Reaction to hydrochloric acid

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The mineral quartz often exhibits good crystal
form
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Pyrite (fools gold) displays metallic luster
Figure 2.10
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Mohs scale of hardness
Figure 2.12
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Three examples of perfect cleavage fluorite,
halite, and calcite
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Conchoidal fracture
Figure 2.15
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Mineral groups

• A few dozen minerals are called the rock-forming
  minerals
• The eight elements that compose most rock-forming
  minerals are oxygen (O), silicon (Si), aluminum
  (Al), iron (Fe), calcium (Ca), sodium (Na),
  potassium (K), and magnesium (Mg)
• Most abundant atoms in Earth's crust are oxygen
  (46.6 by weight) and silicon (27.7 by weight)

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Composition of continental crust
Figure 2.16
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Mineral groups

• Rock-forming silicates
• Most common mineral group
• Contain the silicon-oxygen tetrahedron (molecule)
• Four oxygen atoms surrounding a much smaller
  silicon atom
• Combines with other atoms to form the various
  silicate structures

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The silicate (SiO4)-4 molecule
Figure 2.17
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Mineral groups

• Rock-forming silicates
• Groups based upon tetrahedral arrangement
• Olivine independent tetrahedra
• Pyroxene group tetrahedra are arranged in
  chains
• Amphibole group tetrahedra are arranged in
  double chains

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Hornblende a member of the amphibole group
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Mineral groups

• Rock-forming silicates
• Groups based upon tetrahedral arrangement
• Micas tetrahedra are arranged in sheets
• Two types of mica are biotite (dark) and
  muscovite (light)
• Feldspars - Three-dimensional network of
  tetrahedra

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Mineral groups

• Rock-forming silicates
• Groups based upon tetrahedral arrangement
• Feldspars
• Feldspars are the most abundant mineral group
• Crystallize from molten material
• Two types of feldspar are Orthoclase and
  Plagioclase
• Quartz three-dimensional network of tetrahedra
  

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Potassium feldspar
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Plagioclase feldspar
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Mineral groups

• Nonsilicate minerals
• About 8 of Earths crust
• Have important economic value
• Major groups
• Oxides
• Sulfides
• Sulfates
• Carbonates
• Native elements (single elements)
• Gold, copper, diamond, silver, etc.

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Native Copper
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Mineral groups

• Nonsilicate minerals
• Carbonates
• A major rock-forming group
• Found in the rocks limestone and marble
• Halite and gypsum are found in sedimentary rocks
• Many have economic value

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Thick bed of Halite (salt) At an under- Ground
mine
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Sapphires showing variations in cuts and colors
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Mineral resources

• Earths storehouse of useful minerals that can be
  recovered for use
• Reserves include
• Already identified deposits of useful minerals
  that can be extracted profitably
• Known deposits not yet recoverable under present
  conditions
• Ores are useful metallic minerals that can be
  mined at a profit
• Industrial rocks and minerals
• Materials for building stone, road paving,
  fertilizers, etc.
• Economic factors may change and influence a
  resource
• E.g., is there enough concentration of gold to
  warrant excavation?
• To be of value an element would exist in a
  deposit that is far above its natural
  concentration level

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An underground halite (salt) mine