Rocks

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Rocks
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Rocks

• Rocks are classified by how they formed and what
  theyre made of
• There are 3 general classes of rocks
• Igneous
• Sedimentary
• Metamorphic

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Igneous Rocks
Are formed when lava and magma cool to form solid
rock
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Igneous Rocks

• Extrusive are formed once magma reaches the
  surface and cools
• Ex basalt, pumice
• Intrusive are formed from magma that cools and
  solidifies within the crust, which may later be
  uncovered by the process of erosion
• Ex granite gabbro

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Sedimentary Rock
Are formed when sediments (sand clay, and silt)
are compressed and become solid rock
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Sedimentary Rock

• Formed by wind, water, snow or organisms breaking
  down other rocks into sediments
• Most sediments are deposited on the bottom of
  lakes, rivers and seas, and then compressed to
  form rock.
• Cover about 75 of Earths surface
• Many sedimentary rocks have been moved by water,
  wind, waves, currents, ice or gravity.

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sandstone
shale
limestone
Common examples
Halite (rock salt)
chalk
coal
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Metamorphic Rocks
Metamorphic rocks form when existing rocks are
heated or squeezed they recrystallize and might
change chemically.
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Metamorphic Rocks

• All kinds of rocks can be changed
• Can change the crystal structure, texture, or can
  form new minerals

marble
limestone
gneiss
granite
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Rock Cycle
In the rock cycle, rocks change from one type to
another over millions of years. A rock in any
part of the cycle could become any other kind of
rock.
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cementation
Weathering and Erosion
Rock Cycle
Heat and Pressure
Cooling and Hardening
Melting
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Minerals
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Minerals
A mineral is an inorganic solid material with a
particular chemical makeup and orderly
arrangement of atoms.
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Minerals

• Rocks are usually composed of two or more
  minerals.
• Minerals form from hardening of magma or lava
• Mineral formation clues include size and how
  mineral crystals fit together.
• Solid materials with a repeating pattern of
  atoms are called crystals.

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Properties/Characteristics to Identify Minerals

• Cleavage- splitting into thin sheets
• Fracture- breaking into rough edges
• Color- many different colors, not mineral
  specific
• Shape (habit)- special arrangement of atoms, if
  grown unimpeded
• Luster- describes how light reflects from a
  minerals surface.

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Properties/Characteristics to Identify Minerals

• Streak- is the color powder produced when a
  mineral is scratched on an unglazed white tile.
• Hardness- Mohs scale is used to classify
  minerals from 1 (softest, talc) to 10 (hardest,
  diamond). It is also a test of which minerals
  scratch or are scratched by others.

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Properties/Characteristics to Identify Minerals

• Other properties of minerals include magnetism,
  double refraction, taste, or reactions with acid.

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Common Minerals
Rare minerals which can be cut and polished are
gems. This makes them ideal for jewelry.
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Common Minerals
An ore contains enough useful mineral to be sold
at a profit. Copper is an example of an ore.