Minerals, Rocks, and Weathering & Erosion

• Minerals


  Naturally-occurring, inorganic, homogeneous solid, with a definite chemical composition, and ordered internal structure
• Mnemonic for mineral properties: N-I-H-D-O
• Inorganic

  Must not be composed of the complex hydrocarbon molecules that are the basis of life-forms
• Naturally-occurring

  A mineral must form through natural geologic processes
• Crystalline solid


  The atoms that make up the mineral are arranged in an orderly, repeating, three-dimensional pattern
• Definite chemical composition

  Definite chemical formula
• Physical properties of minerals

  • Color
  • Streak
  • Luster
  • Hardness
  • Cleavage
  • Fracture
  • Odor
  • Taste
  • Magnetism
• Hardness


  The ability of a mineral to resist scratching or abrasion
• Cleavage


  The ability to break, when struck/split, along preferred planal directions
• Fracture


  The rough and irregular breakage of a mineral
• Ore minerals

  Metallic and some nonmetallic minerals which contain useful substances that can be mined for a profit
• Minerals


  Naturally-occurring, inorganic, crystalline solid that has a specific chemical composition
• Rocks

  Naturally-formed aggregates of minerals or mineral-like substances
• Types of rocks

  • Igneous
  • Sedimentary
  • Metamorphic
• Igneous rocks


  • Formed when magma or lava cools and solidifies
  • The study of igneous rocks provides us with an insight into the composition of Earth's mantle and the processes that cause it to melt
• Types of igneous rocks

  • Extrusive
  • Intrusive
• Extrusive igneous rocks


  Formed when magma solidifies at the surface
• Intrusive igneous rocks


  Formed when magma solidifies beneath the surface
• Igneous rock classification

  • Intrusive/Plutonic
  • Extrusive/Volcanic
  • Pyroclastic
• Intrusive/Plutonic igneous rocks

  Coarse-grained igneous rocks formed when magma solidifies far below the surface so that the cooling was slow enough to enable the large crystals to grow
• Extrusive/Volcanic igneous rocks

  Fine-grained igneous rocks formed when magma solidifies at or near the surface so that the cooling is rather rapid; there is little time for crystals to form, so extrusive igneous rocks have tiny crystals
• Pyroclastic igneous rocks

  Rocks formed from pieces of other rocks, animal/plant remains, or minerals
• Pyroclastic igneous rock examples

  • Scoria
  • Pumice
  • Tuff
  • Obsidian
• Conditions for magma formation

  • Increase in temperature
  • Decrease in pressure
  • Addition of volatiles
• Sedimentary rocks


  Rocks that were formed from weathered and eroded remains of preexisting rocks, precipitation from solutions, or animal/plant remains
• Lithification

  General term for the processes that convert loose sediments into sedimentary rocks, including compaction, cementation, and crystallization
• Types of sedimentary rocks

  • Detrital
  • Chemical
  • Organic
• Detrital sedimentary rocks


  Formed from weathered and eroded remains of preexisting rocks
• Chemical sedimentary rocks

  Deposited by precipitation of minerals from a solution
• Organic sedimentary rocks

  Composed of organic molecules (Carbon)
• Metamorphic rocks


  Rocks that were formed from exposure to extreme heat and pressure in the crust
• Types of metamorphism

  • Contact
  • Regional
• Contact metamorphism

  Involves existing rocks coming into contact with intense heat
• Regional metamorphism


  Occurs when rocks are buried deep in the crust, commonly associated with convergent plate boundaries and the formation of mountain ranges
• Classification of metamorphic rocks

  • Foliated
  • Non-foliated
• Foliated metamorphic rocks

  Have a layered or banded appearance due to exposure to heat and direct pressure
• Non-foliated metamorphic rocks

  Do not possess a layered or banded appearance, and minerals are not preferentially-aligned
• Rock cycle

  Shows the interrelationship between igneous, sedimentary, and metamorphic rocks, and how rocks move from deep to shallow, and from high to low temperatures and pressures, in response to tectonic forces and isostasy
• Weathering

  The process that changes the physical and chemical character of a rock at or near the surface
• Types of weathering

  • Physical
  • Chemical