Minerals

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Minerals

• 5.2 Composition and Structure of Minerals

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What is a mineral?

• A mineral has the following characteristics
• It occurs naturally.
• It is a solid.
• It has a definite chemical composition.
• Its atoms are arranged in an orderly pattern.
• It is inorganic (never alive or produced by
  something that was alive.)

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Minerals
Name Symbol
Oxygen O 46.6
Silicon Si 27.7
Aluminum Al 8.1
Iron Fe 5.0
Calcium Ca 3.6
Sodium Na 2.8
Potassium K 2.6
Magnesium Mg 2.1
Other - 1.5

• There are about 4000 known minerals
• Examples) gold, quartz, halite (salt), diamond
• 8 elements make up 98.5 of the crusts total
  mass.
• Most minerals are compounds.

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Minerals Through the Magma Process

• Many minerals form out of molten rock.
• In magma, atoms or ions can move freely.
• As magma cools the atoms, molecules and ions move
  closer together and form chemical bonds that
  create compounds.
• Many different minerals can form from the same
  magma mass.
• The types of minerals that form depend on
• The types of elements present in the magma
• The rate at which the magma cools determines the
  crystal size.

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Minerals Through the Pressure Process

• When a rock is subjected to high temperature and
  pressure, the minerals begin to break down
  chemically.
• The temperature and pressure becomes great enough
  to change the mineral in a solid state.
• The free atoms, ions, and molecules recombine
  forming new minerals.

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Structure of Minerals

• Minerals form crystals.
• A regular geometric solid with smooth surfaces
  called crystal faces.
• Contain a regularly, orderly arrangement of
  atoms.
• Although there are thousands of different
  minerals, there are only 6 basic different shapes
  of crystals.

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Six Crystal Systems
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Silicates

• Silicon and oxygen are the two most abundant
  elements in the Earths crust.
• Most minerals (90) contain these two elements
  and are called silicates.
• A silicate may contain one or more metallic
  elements.
• The basic building block of a silicate is the
  silicate tetrahedron.
• Consists of 4 oxygen atoms around a silica atom.
• Named for its shape.

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Silica Tetrahedron