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versus
Rock on!
Igneous Rocks
…are solidified from mineral
matter in a high-temperature
molten state.
Sedimentary Rocks
…are layered accumulations of mineral
particles derived mostly by weathering
and erosion of preexisting rocks.
Metamorphic Rocks
…are formed from rocks that have been
physically or chemically changed, usually by
application of heat and pressure during
crustal mountain-making.
Difference between Minerals and Rocks
• A mineral is a solid, inorganic,
naturally-forming material of the Earth
that has both a known chemical
composition and a crystalline structure
with distinct physical properties that is
unique to that mineral
• A rock is a solid aggregate of one or
more minerals that have been
cohesively brought together by a rockforming process.
http://www.fi.edu/fellows/fellow1/oct98/create/index.html
Igneous Rocks
- ‘Fire’ rocks
- Formed either underground or
above ground.
- Underground, they are formed
when magma becomes
trapped in small pockets and
cool slowly (intrusive)
- Above ground, igneous rocks
form when volcanoes erupt,
causing magma to come to the
surface (called lava) and cools
(extrusive)
Igneous Rock
Observable
Characteristics
Location of
Formation
Example
Volcanic (Extrusive)
Crystals so small you
can't see them with
the unaided eye.
Sometimes there are
larger, visible crystals
in a very fine-grained
matrix.
These rocks were
once liquid magma
that erupted from
volcanoes. They
cooled very quickly,
which is why the
crystals are usually
very small.
Basalt – usually dark
gray to black, finegrained volcanic rock;
sometimes has gas
bubbles (vesicles)
Intrusive
Interlocking Crystals
These rocks were
once liquid magma,
but they did not erupt
from volcanoes.
Instead, they cooled
slowly underground.
The crystals had time
to grow large. We see
them because erosion
has stripped off and
removed all of the
rock above it.
Granite – pinkish,
whitish igneous rock
with interlocking
crystals of quartz and
feldspar. Sometimes
includes mica.
Igneous Rock Classification
Common Igneous Rocks
Classification
Intrusive Igneous
Rocks
Extrusive Igneous
Rocks
Igneous
Rock
Color
Common Minerals
Granite
Felsic
(light-colored)
Quartz, potassium feldspar, plagioclase
feldspar, mica
Diorite
Intermediate
Plagioclase feldspar, amphibole,
pyroxene, mica
Gabbro
Mafic
(dark-colored)
Plagioclase feldspar, pyroxine, olivine
Rhyolite
Felsic
Quartz, potassium feldspar, plagioclase
feldspar, mica
Andesite
Intermediate
Plagioclase feldspar, amphibole,
pyroxene, mica
Basalt
Mafic
Plagioclase feldspar, pyroxine, olivine
Pumice
Felsic/Interme
diate
Various silicates
Obsidian
Variable
Various silicates
http://www.beyondbooks.com/ear82/7a.asp
Sedimentary Rocks
- ‘Water’ rock
- Over millions of years, rocks
are eroded and weathered and
transported by wind and water
to eventually settle in the
bottom of rivers, lakes or
oceans.
- Layer after layer of eroded
earth are deposited on top of
each other.
- These layers are compressed
over time, until the bottom
layers slowly turn into rock
under great pressure.
- These layered rocks that form
are called sedimentary rocks
Sedimentary
Clastic
Chemical
Observable
Characteristics
Made up of smaller
rocks cemented
together. Sometimes
has fossils. Usually
has layers.
Usually a light gray,
sometimes with
crystals, sometimes
with shells,
sometimes just
massive.
Location of
Formation
These rocks formed
when loose sediment
(rocks, sand) were
deposited by water,
compacted, and
cemented together.
These rocks form
along beaches, by
rivers, or under the
water in lake or
oceans.
Example
Conglomerate –
composed of pieces
pebble-size or larger
Sandstone composed of sandsize pieces
Shale - composed of
pieces smaller than
fine sand
These rocks are also
Limestone – a whitish
deposited in water.
or grayish rock made
However, they form
of the mineral calcite.
as a chemical reaction
in the water that
leaves a chemical
deposit, usually on an
ocean bottom.
Sedimentary Rock Classification
Common Sedimentary Rocks
Classificati Sedimentary
on
Rock
Clastic
(Detrital)
NonClastic
(Chemical)
Composition
Depositional Environment
Shale
Clay and/or silt
Swamp, floodplain, river bottom
Sandstone
Sand
Beach, desert
Conglomerat
e
Various-sized
pebbles
Riverbed
Limestone
Calcite or
fragmented shells
Shallow sea, coastline
Chert (flint)
Chalcedony
(quartz), traces of
other minerals
Formed from a silica-rich precipiate
in a deep ocean environment.
Bituminous
Coal
Plant material
Ancient forest or swamp
http://www.beyondbooks.com/ear82/7b.asp
Metamorphic Rocks
- Rocks that have "morphed"
into another kind of rock
- Morphing happens under
tons of pressure, which
fosters heat build up, and
this causes them to
change.
- This explains why some
metamorphic rock samples
have flattened grains.
Metamorphic
Observable
Characteristics
Usually has
interlocking crystals
and layers (called
foliation)
Location of
Formation
These rocks formed
when igneous,
sedimentary, or other
metamorphic rocks
are heated and/or
squished, forming a
new rock type. This
usually happens
during mountain
building events
(regional
metamorphism), but
also happens during
igneous activity
(contact
metamorphism).
Example
Quartzite –
metamorphosed
sandstone
Slate –
metamorphosed
shale.
Schist –
metamorphosed
sedimentary rocks
that had lots of clay.
Gneiss –
metamorphosed
granite.
Metamorphic Rock Classification
Common Metamorphic Rocks
Classificat Metamorph
ion
ic Rock
Foliated
(Banded)
NonFoliated
(Not
Banded)
Parent Rock
Common Minerals
Slate
Shale, mudstone
Quartz, clay
minerals (feldspars)
Schist
Shale, slate, basalt, or granite
Mica, chlorite, talc,
quartz
Gneiss
Shale, schist, granite,
sandstone, and other rock types
Quartz, feldspars
Quartzite
Sandstone
Quartz
Marble
Limestone, dolomite
Calcite
Anthracite
coal
Bituminous coal
Crystalline carbon
http://www.beyondbooks.com/ear82/7c.asp