Composition and Structure of Minerals

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Composition and Structure of Minerals
After completing this section, students will
discover the unique physical characteristics of
various minerals (Standard PI 021)
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All the rocks of the Earths crust consist of
minerals
A mineral has the following characteristics
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Minerals occur naturally

• Minerals are found in the ground, or in water.
  Halite is formed from dissolved seawater

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Minerals are solid

• Many minerals are formed from solidified magma

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Minerals have a definite chemical composition

• Sodium chloride is the chemical formula for halite

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The have atoms arranged in an orderly pattern
(form crystals)

• There are 6 families of crystal families

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Minerals are inorganic (never alive)
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There are over 4000 known minerals. But 8
minerals make up 98 of the earths crust

• More than 90 of the minerals in the earths
  crust are compounds containing oxygen and silicon

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Most minerals are compounds. A compound is a
combination of two or more elements
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A few minerals consist of single elements and are
called native elements
Native gold
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Minerals can form in many ways. Some form from
molten rock (magma)

• As the magma cools, the atoms, ions and molecules
  move closer together and form chemical bonds that
  create compounds

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These are examples of minerals that form from
magma
tourmaline
plagioclase
basalt
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Some minerals from as water containing dissolved
ions slowly evaporates.

• Sylvite forms from sodium and chlorine ions
  dissolved in water

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Still other minerals form from heat, pressure or
chemical action
Copper ore formed from pressurization