Rock Identification

1
Rock Identification

• Igneous, Sedimentary, and Metamorphic Rocks

2
The Rock Cycle
3
Igneous Rocks

• Solidified products of once-molten material
  called magma
• Interlocking arrangement of mineral crystals that
  forms as the molten material cools and crystals
  grow
• Intrusive form below the Earths surface
• Extrusive formed at the Earths surface

4
Identifying Igneous Rocks

• The rate of cooling determines the size of the
  interlocking crystals.
• Slower cooling Larger crystals
• Igneous rocks are identified based on texture.

5
Igneous Textures

• Coarse Grained- Majority of crystals are of a
  uniform size and can be seen without
  magnification.
• Fine Grained- Very small crystals which are
  generally not identifiable without magnification.

6
Igneous Textures

• Polyphyritic- Two very contrasting sizes of
  crystals caused by magma cooling at two different
  rates.
• Glassy- No mineral crystals develop because of
  very rapid cooling.

7
Igneous Textures

• Fragmented- The rock contains broken, angular
  fragments of rocky material produced during an
  explosive volcanic eruption.

8
Sedimentary Rocks

• Form at or near Earths surface from the
  accumulated products of weathering (sediments)
• Lithification transforms the sediment into hard
  rock
• Can be classified as either detrital rocks or
  chemical rocks

9
Detritral Sedimentary Rocks

• Detrital- consists mineral grains or rock
  fragments derived form the process of mechanical
  weathering. Identification is based on the size
  of grain.

10
Chemical Sedimentary Rocks

• Chemical- previously dissolved in water and later
  precipitated by either inorganic or organic
  processes. Mineral composition is used to
  identify.

11
Metamorphic Rocks

• Forms below Earths surface with high
  temperatures and pressures.
• Rocks are identified by both texture and
  composition.