Download Igneous Rocks

Unit D Chapter 2
“Rocks and the Rock Cycle”
Lesson 1 Pgs D40-D45
Minerals
Minerals are the building
blocks of rocks.
 A Mineral is a natural
solid substance that has
a definite chemical
composition and
physical structure.
 There are more than
4000 minerals, but only
about a dozen are
common.
 Minerals make up most
of the rock in earth’s
crust.

Quartz is one of the most common
rock forming minerals. Combined
with feldspar, it makes granite, the
most common rock on earth.
Some people believe (not kidding) that
quartz balances your physical, mental,
emotional, and spiritual planes. Not only
that, but can enhance your organs, memory
and even psychic ability! In reality land,
your are just holding a rock.
Minerals


Scientists identify
minerals by their
properties.
Some of the
properties are
hardness, color,
crystal shape,
density, and the
color it leaves when
scraped on tile.
Diamonds are the hardest
minerals on the planet. The Hope
Diamond is a blue diamond
weighing at 45.52 carats.
Chalk is a very soft mineral and very common.
Formation of Igneous Rocks
Melted rock within the
Earth’s mantle is
called magma.
 Igneous rock is
formed when magma
pushes up through the
crust and hardens into
rock.
 Magma that reaches
the surface is called
lava.
 There are two types of
igneous rock; intrusive
and extrusive.

If this is your view of lava, consider
taking a few steps back.
Intrusive Igneous Rock

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
Intrusive Rock is
formed when magma
hardens inside Earth’s
crust.
Intrusive rock is also
sometimes called
plutonic rock after
Pluto, the Greek god
of the underworld.
(Before you yell out “It
was Hades!!” I’ll
explain.)
These intrusive rocks
can be called Plutons.
Granite is an intrusive rock. The granite
boulders in Elephant Rocks State Park are
a great place to see plutonic rock.
Intrusive Igneous Rock



Intrusive rocks cool
slowly because they
form underground.
This gives crystals
longer to form so
intrusive rocks
typically have large
crystals.
Large plutons that get
exposed by erosion
are called batholiths.
They can be as large
as mountains.
This batholith is called Shiprock in New
Mexico. It is the hardened core of an
extinct volcano. The rest of the volcano
eroded away, leaving the hardened magma
behind.
Extrusive Igneous Rocks
Extrusive Rock is
formed when lava
cools quickly on
Earth’s surface.
 Because they cool
quickly, crystals do not
have much time to
form.
 Because of this,
extrusive rocks have a
fine-grained texture.
 Some examples of
extrusive rock include
obsidian and pumice

Pumice forms with millions of
bubbles making it so light, that it is
the only rock that can float!
Obsidian forms as
a black, volcanic
glass.
Uses of Igneous Rocks


Because igneous
rocks are some of the
most common on
Earth, they are used
in many things.
Granite is a strong,
durable rock used for
building materials.
The Empire State
Building and The
Great Wall of China
are made from
granite.
Uses of Igneous Rocks
Obsidian has been used
for tools and jewelry.
 Obsidian breaks with a
sharp edge and was
used for cutting tools.
 Pumice is ground into a
powder for scouring
substances in soaps
and powders.
 It was even used as a
tooth cleaner but had
the side effect of filing
down the teeth to little
nubs.

Uses of Igneous Rocks

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Igneous rocks are
also sources of
valuable ores.
Ores are useful
minerals or mixtures
of minerals that are
mined.
These ores contain
chromium, platinum,
diamond, nickel and
copper.
Platinum in its
raw form.
Real diamond
ore.
Not so real
diamond ore.