MINERALS

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MINERALS

• Definition of a mineral
• It is naturally occurring
• It is a solid substance
• It has orderly crystalline structures
• Definite chemical composition
• Generally considered inorganic

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• How minerals form
• There are 4 major processes by which minerals
  form
• crystallization from magma,
• precipitation,
• changes in pressure and temperature,
• and formation from hydrothermal solutions.

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• Crystallization from magma
• As magma cools, elements combine to form mineral
  crystals (like hot sugar water allowed to cool).
  As minerals continue to form, the composition of
  the magma changes. Minerals rich in sodium,
  potassium, and aluminum then form.

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• Precipitation
• The minerals left behind, or precipitated
  (settle) out of water.
• Example- limestone cave formation is formed
  through precipitation.

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• Pressure and Temperature
• An increase in pressure can cause minerals to
  recrystallize while still solid (carbon -gt
  diamonds)
• An increase in temperature causes instability in
  minerals and they change form to become more
  stable again

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• Hydrothermal solutions
• Hydrothermal solutions are very hot mixtures of
  water and dissolved substances . When they come
  in contact with existing minerals, they form a
  new mineral through chemical reactions.

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• Mineral Groups
• Mineral Groups can be classified based on their
  composition .
• There are over 3800 minerals that have been
  named, but we will focus only on the most
  abundant of these minerals.

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• Silicates
• Silicon and oxygen combine to form a structure
  called the silicon-oxygen tetrahedron.
• This silicon-oxygen tetrahedron provides the
  framework of every silicate mineral.

Quartz is the most common silicate mineral.
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• Carbonates
• Carbonates are minerals that contain the elements
  carbon, oxygen and one or more metallic elements.

Calcite is the most common carbonate mineral
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• Oxides
• Oxides are minerals that contain oxygen and one
  or more other elements, which are usually metals.

Rutile forms as magma cools deep beneath Earths
surface.
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• Sulfates and Sulfides
• Sulfates and sulfides are minerals that contain
  the element sulfur.
• Halides
• Halides are minerals that contain a halogen (Cl,
  F, etc) ion plus one or more other elements.

Anhydrite is a sulfate
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• Native Elements
• Native elements are minerals that exist in
  relatively pure form.
• Examples include gold, silver, copper, carbon and
  sulfur.

Gold in various forms
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PROPERTIES OF MINERALS

• Minerals vary in their properties and so the
  characteristics of these different properties are
  used to classify minerals into various groups.

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• Color
• Color is defined by the small amount of different
  elements which give the same materials their
  color.
• Streak
• Streak is the color of the mineral in its
  powdered form.

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• Luster
• Luster is used to describe how light is reflected
  from the surface of a mineral.
• Crystal Form
• Crystal form is the visible expression of a
  minerals internal arrangement of atoms.

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• Hardness
• Hardness is a measure of the resistance of a
  mineral to being scratched.
• Cleavage
• Cleavage is the tendency of a mineral to cleave,
  or break, along flat, even surfaces.

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Other minerals may be magnetic (magnetite),
Glow in ultraviolet light (fluorite),
Or cause double images! (calcite)