Minerals and Rocks

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Minerals and Rocks
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Rocks

• Aggregates (mixturecan be separated) of minerals.

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Minerals

• Four Characteristics
• Naturally occurring
• Inorganic (was never alive)
• Solid
• Possesses a definite chemical structure

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Properties of Minerals

• Crystal formexternal expression of internal
  structure

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Properties of Minerals

• Colorunreliable in identifying minerals

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Properties of Minerals

• Streakthe color of a mineral in its powder
  formobtained by rubbing the mineral across a
  hard, unglazed porcelain

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Properties of Minerals

• Hardnessresistance of a mineral to abrasion or
  scratching
• Mohs scalehardness scale ranging from 10
  (hardest) to 1 (softest)
• Diamond is 10, talc is 1

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Properties of Minerals

• Cleavagetendency of a mineral to break along
  planes of weak bonding

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Properties of Minerals

• Fracturedo not exhibit cleavage when broken
• Specific gravitythe weight of a mineral compared
  to the same volume of water

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Mineral Groups

• Silicates
• Silicon and oxygen are the two most abundant
  elements in the Earths crust they form
  silicates
• All have the same basic structurethe
  silicon-oxygen tetrahedronfour oxygen atoms
  surrounding a silicon atom
• Other elements join the tetrahedrons together in
  chains, sheets, or three-dimensional networks.
• Feldspars are most abundant, with quartz second

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Mineral Groups

• Carbonates
• Calcite
• Limestoneused in building and paving
• Marbleused decoratively
• Halite (salt) and Gypsum also found in
  sedimentary rock

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Mineral Resources

• Reservesalready identified deposits from which
  minerals can be extracted profitably
• Oresuseful metallic minerals that can be mined
  at a profit
• Changing economic factors determine whether a
  deposit is profitable to extract