Minerals of the Earths Crust

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Minerals of theEarths Crust

• What is a Mineral?
• Identifying Minerals

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Thought Questions

• What is a mineral? Name two minerals you know.
• How do minerals form?
• What elements do you think are most commonly
  found in minerals?

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Chapter 4 Objectives

• Distinguish between the two main mineral groups
• Identify the elements most abundantly found in
  common minerals
• Name six types of nonsilicate minerals
• Distinguish among the six main arrangements of
  silicon-oxygen tetrahedra found in silicate
  minerals
• Describe some characteristics that help
  distinguish one mineral from another
• List four special properties that help to
  identify certain minerals

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What is a Mineral?

• Mineral- the basic material that make up the
  rocks and crust of the earth naturally
  occurring,usually inorganic, with a specific
  chemical composition, an orderly chemical
  structure, and specific characteristic properties
• Inorganic-non-carbon bearing material not made
  of or from living organisms or once living
  organisms

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Mineral or Not?

• To determine if a substance is a mineral, it must
  fit into four basic categories. Mineralogists ask
  the following four questions to identify
  minerals
• Is the substance inorganic?
• Does the substance occur naturally?
• Is the substance solid with a regular crystalline
  form?
• Does the substance have a regular, repeating
  chemical composition?

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How Minerals Form

• There are four ways that minerals form
• Crystallization within magma (i.e. tourmaline,
  olivine, quartz, feldspar)
• Precipitation from solution (salt flats)
• Changes in pressure or temperature
• Formation form hydrothermal solutions

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Mineral Characteristics

• Definite Crystalline Structure
• At times and fairly rare, a mineral will form in
  an open space and grow into one large crystal,
  possibly taking the shape of one of the six major
  crystal systems.

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Classifying Minerals

• Rock-Forming Minerals-minerals that form the
  rocks of the earths crust 20 total 10 make up
  90 of the earths crust (quartz, orthoclase,
  plagioclase, muscovite, biotite, calcite,
  dolomite, halite, gypsum, and ferromagnesian
  minerals)
• Two major groups based on chemical composition
• Silicates-minerals that contain silicon and
  oxygen 96 of earths crustal rocks
• Nonsilicates-minerals that do not contain any
  silicon only 4 of the earths crustal rocks
  organized into 6 major groups

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Mineral Groups
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Some Rock-Forming Minerals
Muscovite
Plagioclase Feldspar
Orthoclase Feldspar
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Major Classes of Nonsilicates
Calcium Carbonate
Carbonates - Contain carbonate group, CO3 Halides
- Compounds that have The metals Sodium,
Potassium, or Calcium combined with Chlorine or
Fluorine Native Elements - Elements found pure in
nature. Oxides - Compounds with Oxygen and an
element other than Silicon. Sulfates - Compounds
containing sulfate, SO3. Sulfides - Compounds
that consist of one or more elements combined
with sulfur.
Fluorite (halide)
Copper Ore (native element)
Hematite (oxide)
Gypsum (sulfate)
Pyrite (sulfide)
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Non-Silicate Examples
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Crystalline Structure

• Crystal-any solid whose atoms, ions or molecules
  are arranged in a regular, repeating pattern
• Silicon-Oxygen Tetrahedron-the base crystalline
  structure that makes up all silicate minerals
  arranged in six basic structures
• Isolated Tetrahedra
• Ring Silicates
• Single Chain Silicates
• Double Chain
• Sheet Silicate
• Framework Silicates

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Mineral Groups

• Silicates

• One silicon atom attaches to four oxygen atoms to
  form a silica tetrahedron, a three-dimensional
  shape structured like a pyramid.

• The basic silica tetrahedron has the ability to
  share oxygen atoms with other tetrahedron
  molecules.
• This allows the molecules to combine chemically
  and structurally in a vast number of ways.

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Mineral Groups

• Silicates

• Some possible arrangements formed by silica
  tetrahedrons include single chains, double
  chains, and sheets.

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Section Assessment

• Match the following terms with their
  definitions.
• ___ mineral
• ___ crystal
• ___ magma
• ___ silicate

B C D A
A. minerals that contain silicon and oxygen, and
usually one or more other elements B. a naturally
occurring, inorganic solid with a specific
chemical composition and definite crystalline
structure C. a solid in which the atoms are
arranged in repeating patterns D. molten material
found beneath Earths surface
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Section Assessment

• Identify whether the following statements are
  true or false.

_______ There are about 30 common minerals in
Earths crust. _______ Slowly cooling magma
produces small crystals. _______ Coal is a
mineral. _______ Silicates are the most common
minerals on Earth. _______ Well-defined crystal
shapes are rare.
true false false true true
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Studying Minerals

• Mineralogist-Geoscientist that examine, analyze,
  and classify minerals
• Physical Properties of Minerals All minerals
  have a specific set of characteristic properties
  unique to that mineral bases on the chemical
  composition and crystalline structure there are
  seven distinguishing properties

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Seven Mineral Characteristics

• Color- the color of the mineral
• Streak-the color of the mineral in powder form
  observed by rubbing the mineral against an
  unglazed ceramic tile (streak?color)
• Luster-the light that is reflected from a
  minerals surface
• Metallic-highly reflective, shiny (like polished
  metal)
• Nonmetallic-dull, non reflective material
• Cleavage-the tendency of a mineral to break/split
  along specific planes of weakness to form smooth,
  flat surfaces often expressed as an angle degree

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Color, Luster and Cleavage
Quartz comes in a variety of colors
Metallic and Dull Luster
Fracture
Examples of mineral cleavage
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More Mineral Characteristics

• Fracture-minerals that break in inconsistent
  patterns, forming irregular, uneven pieces with
  curved or jagged edges
• Hardness-the measure of the ability of a mineral
  to resist surface scratches independent of
  fracture or cleavage
• Mohs Hardness Scale-the standard scale against
  which the hardness of minerals is tested bases
  on 1-10 with 1 the softest and 10 being the
  hardest

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Last of the Characteristics

• Crystalline Shape-all minerals form in one of six
  basic shapes specific minerals always form the
  same crystalline shape
• Density-the ratio of the mass of a substance to
  its volume specific to mineral type

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Special Mineral Properties

• Fluorescence-minerals that glow under
  ultraviolet light
• Phosphorescence-rocks that continue to glow
  even after an ultraviolet light is removed
• Magnetism-some minerals are magnetic

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More Special Properties

• Refraction-transparent minerals that bend light
  as it passes through the mineral creating a view
  through the mineral
• Double refraction-two images produced
• Radioactivity-minerals whose atoms are unstable
  release high energy particles