Sire Kassama
2014
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Igneous: granite, basalt, crystallize from hot
molten rock
There are two main types of igneous rock:
intrusive and extrusive
Meteorites; igneous rocks from space
Cinder: small chunks of rock about the size
of a grape that solidify in the air; full of holes
made by gas bubble
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Igneous rock never contain fossils and are
normally hard
Volcanic bombs happen when small pieces of
lava blast through air at high speed and cool
very rapidly, most turn to volcanic ash and
some form pumice which is light enough to
float on water
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Phaneritic: size of grains are large enough to
see unaided; characterized by slow cooling in
plutonic environment
Aphanitic: grain size is too small to see with
naked eye; characterized by rapid cooling in
volcanic environments
Porphyritic: rock has distinct differences in
the size of crystals
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Any igneous rock made on the surface of the
volcano
Grains are too small to see because magma
cooled quickly on earth’s surface and crystals
do not have time to grow large and call these
rocks fine grained
Sometimes lava cools so rapidly that no
crystals grow and instead the lava turns to a
glass like rock called obsidian or volcanic
glass
Examples: rhyolite, andesite, obsidian
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Also known as Plutonic Rocks
Any igneous rock made underground
Characterized by coarse grains in rocks
Crystal minerals are large enough to see
because magma cools slowly which gives
crystals time to grow and call these rock
coarse grained
Examples include: granite, gabbro, diorite
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Cooled and solidified at a
considerable depth
Visual appearance reveals
interlocking crystals forming
the rock mass
Characterized by large crystal
sizes
Cooling and hardening is
typically quite slow
Surface feels relatively rough
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Characterized by finegrained textures
Formed at or above the
surface of the planet
Cooling and hardening is
typically quite rapid
Surface feels relatively
smooth
Both
• Silica is the most abundant component
• Named and identified on the basisExtrusive
of composition and texture
Intrusive
• Formed from the crystallization of minerals
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Contain feldspar minerals
May become transformed into sedimentary rocks when exposed to the Earth’s
surface
Rock
Grain Size
Color
Granite
Coarse
Light
Gabbro
Coarse
Dark
Pegamite
Very coarse
Light and dark
Basalt
Fine
Dark
Rhyolite
Fine
Light
Andesite
Fine
Medium
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The diagrams below show the crystals of four
different rocks viewed through the same
hand lens. Which crystals most likely formed
from molten material that cooled and
solidified most rapidly?
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ROCK NAME
TYPE ( Igneous, Sedimentary, metamorphic)
FORMATION
Igneous (Extrusive, Intrusive) (volcanic, plutonic) (felsic or mafic)
Sedimentary ( Clastic, chemical, biochemical, organic)
Metamorphic (Regional, Contact Metamorphism) (low grade-high grade)
ENVIRONMENT
TEXTURE
Igneous (phaneritic, aphanitic, porphyritic)
Sedimentary (grain size)
Metamorphic Foliated or non-foliated
HARDNESS RANGE
MINERALS
PHYSICAL DESCRIPTION
(Color)
USES
OTHER PROPERTIES
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Is an extrusive igneous rock
Forms from Felsic
Found where there are explosive volcanoes
along subduction boundaries
Has small crystals
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Is intrusive igneous rock
Sometimes called black granite
Could occur as dikes or sills as it hardens in
the ground
Normally dark and mottled in appearance
Minerals: plagioclase and hornblende
It’s extrusive form is andesite
Hardness: 7
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It is the most
abundant of Earth’s
Volcanic Rocks and
major component of
ocean’s crust
Fine grained
Dark colored
Low viscosity (runny)
Moon’s dark patches
Minerals: augite and
plagioclase
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Common extrusive
igneous rock
Made from solidified
lava
Sometimes made
from volcanic bombs
Hardness: 6-7
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Extrusive igneous
rock
Degrades over time
Black and sharp with
frosted glassy
surface
Used for surgical
blades but was once
important in
ceremonial and
sacrificial knives
Found in young lava
flows
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Minerals: quartz and
feldspar
Hardness: 5.5
Often found with
pumice
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Intrusive Igneous Rock
Forms from mafic type magma
Is the intrusive form of basalt
Normally very dark color
Commonly made into countertops
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Extrusive igneous rock
Made from thick sticky lava
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Igneous rock sometimes containing crystals
of beryl and garnet
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Igneous Rock
Some giant stones of Stonehenge are dolerite
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Intrusive igneous rock
Made of mostly quartz, feldspar and mica
Pink and white; coarse grained rock
Found in India, Italy, US
Used in Mt. Rushmore and buildings
Appears in huge bubbles of cooling magma
called batholiths
Hardness: 6
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Extrusive igneous rock
Vesicular because gases escaped from the
lava when cooled
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Extrusive Igneous
Rocks
Has volcanic origin
vesicular because
gases escaped from
the lava when cooled
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Can be related to
rhyolite with its
composition
Used to make
building blocks,
concrete, toothpaste,
cosmetics, and soap
Can float in water
Often found with
obsidian
Hardness: 6
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The following questions and answers are
from the New York State Regents Website:
http://www.regentsprep.org/Regents/core/q
uestions/topics.cfm?Course=ESCI
Geology.com