Download Igneous Rocks

THE ROCK CYCLE
(Click on a rock to find out more)
Igneous Rocks
• Igneous Rocks are formed by heat from
magma (which is molten rock beneath the
earth's surface), and are usually associated with
volcanoes.
– There are 2 types of igneous rocks - plutonic and
volcanic.
• Plutonic rocks are igneous rocks that from
deep beneath the earth's surface. The molten
magma cools very slowly forming large
crystals in rocks such as granite.
• Volcanic rocks are igneous rocks that form
above the earth's surface. They cool quickly
and form small crystals. Example are basalt
(made from lava) and pumicestone (formed
when lava is forcefully ejected from a volcano
and air bubbles form within the rock).
Igneous Rock example (basalt)
Sedimentary Rocks
• Sedimentary rocks are rocks formed by the
deposition, compaction and cementing of
small particles (such as silt, sand and
pebbles). These particles are deposited in
layers or strata.
• The compaction of these sediments is
caused by the weight of more sediments laid
down on top of them.
• The cementation is caused by the hardening
of calcium carbonate which is the chemical
that makes up shells and coral.
TYPE OF
SEDIMENTARY ROCK
Conglomerate
Sandstone
PARTICLES OF WHICH
ROCK IS COMPOSED
Sand, pebbles (similar to
concrete)
Sand
Shale (or Mudstone)
Silt or Mud
Limestone
Crushed shells or Coral
Sedimentary Rock
METAMORPHIC ROCKS
• Metamorphic rocks are any rocks that
have been changed by heat and
pressure of volcanic or other earth
movements.
• Metamorphic rocks may have originally
been either sedimentary or igneous or
metamorphic rocks.
NAME OF
TYPE OF
METAMORPHIC
ORIGINAL ROCK ORIGINAL ROCK ROCK
Shale
Sedimentary
Slate
Sandstone
Sedimentary
Quartzite
Limestone
Sedimentary
Marble
Granite
Igneous
Gneiss
Metamorphic rock example
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IDENTIFYING
MINERALS
Color
The main color
Colour is not a reliable guide as some colours are caused by small amounts
of impurities
Lustre
The shininess or dullness of the surface
Lustre can be earthy (dull), vitreous (glassy), brilliant (shiny), pearly
(shiny but not glossy), metallic (like a shiny metal)
Streak
The colour of the powdered mineral
Scratch the mineral on a tile and observe the colour left on the tile
Cleavage and Fracture
This is how the mineral breaks. Fracture can be uneven (rough), even
(nearly smooth), and conchoidal (curved lines where the mineral was hit).
If it breaks along a smooth surface, this is due to cleavage. Different
minerals show either none, one, two or three cleavages.
Hardness
A mineral can be scratched by something harder than it is. Hardness can be
of 5 types - very soft (scratched by a fingernail), soft (scratches fingernails
but not coins), medium (scratches a coin but not a knife blade), hard
(scratches a knife blade but not glass), and very hard (scratches glass)
• http://www.classzone.com/books/earth_sci
ence/terc/content/investigations/es0602/es
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