Rocks

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Rocks
Mt. Rushmore is made from granite an igneous
rock
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Rocks can be put into one of 3 categories
based on how they were created
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These 3 types are
Sedimentary Rock
Igneous Rock
Metamorphic Rock
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SEDIMENTARY ROCKS

• 3 things need to happen
• FIRST an existing rock must be weathered and
  ERODED by for wind and/or water over a long time.
  
• SECOND sediments must gather
• THIRD pressure gets added to the sediments to
  squeeze layers of sediment together
• Layers are deposited on top of lower layers.
  Lower layers become ROCK.

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Shale

• Shale is a type of sedimentary rock formed from
  mud and clay that is compacted together by
  pressure.
• It is used to make bricks and other material that
  is fired in a kiln.

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Limestone

• Limestone is a sedimentary rock made from the
  mineral calcite which came from the beds of
  evaporated seas and lakes and from sea animal
  shells.
• This rock is used in concrete and is an excellent
  building stone for humid regions.

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Sandstone

• Sandstone is a sedimentary rock made from small
  grains of the minerals quartz and feldspar.
• It exists in layers as seen in this picture.
• It is often used as building stones.

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Conglomerate

• Conglomerate is a sedimentary rock with large
  sediments like gravel, sand and pebbles combined
  with clay.
• It is often formed during or immediately after a
  large storm.
• The sediment is so diverse that pressure alone
  cannot hold the rock together it is also
  cemented together with dissolved minerals.

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Gypsum

• Gypsum rocks are sedimentary. Sulfate minerals
  combine as sea water evaporates in large basins.
  
• It is very soft and is used to make Plaster of
  Paris, casts, molds, and Drywall.

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IGNEOUS ROCK

• Igneous rocks form either underground or above.
• Underground, magma becomes trapped in pockets.
  As these pockets of magma cool, Intrusive igneous
  rocks form.
• When volcanoes erupt, magma rises above the
  earth's surface. Magma above the earth is
  called lava.
• Extrusive Igneous rocks are formed as the lava
  cools above ground.

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Granite

• Granite (Intrusive igneous) formed by slowly
  cooling pockets of magma trapped beneath the
  earth's surface.
• Granite is used for long lasting monuments and
  for trim and decoration on buildings.

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Pumice

• Pumice (Extrusive igneous) forms when lava cools
  quickly above ground. You can see where little
  pockets of air had been.
• This rock is light. Many pumice rocks will
  actually float in water.
• Pumice is actually a kind of glass and not a
  mixture of minerals.

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Obsidian

• Extrusive igneous rock high in Silica.
• Obsidian is actually glass and not a mixture of
  minerals.
• Sand or sandstone was melted to form this rock.
• The edges of this rock are very sharp.
• Obsidian has Concoidal cleavage.

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METAMORPHIC ROCK

• have "morphed" (changed) into another kind
  of rock. - were once igneous or sedimentary
  rocks.
• tons and tons of pressure, (which fosters heat
  build up), or a nearby heat source causes
  change, WITHOUT ENTIRELY MELTING.
• If you examine metamorphic rock samples closely,
  you'll discover flattened original grains in the
  rock and bands.

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Schist

• Schist can be formed from basalt, an igneous
  rock shale, a sedimentary rock or slate, a
  metamorphic rock.
• It has flat / planar minerals such as micas,
  talc, and graphite.
• SHISTS provide things like TALCUM POWDER and
  graphite for pencils and printers.

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Gneiss

• Gneiss (nice) rocks are metamorphic. They were
  once granite. Heat pressure changed it.
• Original mineral grains were flattened through
  tremendous heat and pressure and are arranged in
  alternating banded patterns.
• BANDS look like sedimentary layers.Metallic
  minerals accumulate near GNEISS. For a mining
  Geologist, it is nice to find GNEISS.

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THE ROCK CYCLE