.
 ROCKS
 All
rocks are made of 2 or more minerals, but
minerals are not made of rocks.
 Rock Words: There are many common names for
rocks and the usually give you an idea of how
big the rock is. Here are a few:
 mountain - huge, giant hunk of rock that is still
attached to the earth's crust, doesn't move, tall
 boulder - large, taller than a person
 ROCKS
 All
rocks are made of 2 or more minerals, but
minerals are not made of rocks.
 Rock Words:
 rock - large, you could get your arms around it
or a bit smaller but it is usually jagged,
broken off a bigger piece of rock
 river rock - round rocks that are along the edge
& at the bottom of fast-flowing rivers
 stone - medium, you could hold it in two hands
 ROCKS
 pebble
- small, you can hold it with two fingers,
could get stuck in your shoe, usually rounded
 sand - made up of tiny pieces of rock, grains of
sand
 grain - tiny, like a grain of rice or smaller, often
found on a beach
 dust - really fine powder that is mixed in with
sand or soil
 speck - as in a speck of dirt
 MINERALS
A
mineral is the same all the way through. That is
one reason we speak of a sample or a specimen
rather than a rock.
 There are about 3000 known minerals on earth.
 All rocks are made up of 2 or more of these
minerals
 Gabbro
is a dark-colored coarse-grained
intrusive igneous rock. The specimen
shown above is about two inches (five
centimeters) across.
 This
table describes the composition of
igneous rocks
 Igneous
rocks are rocks which solidify
from molten material (magma). Cooling
of the magma can occur beneath the
surface (intrusive) or on the surface
(extrusive). Igneous rocks can be
identified by the determination of the
composition and texture of the rock.
Igneous Rock Identification Chart
COMPOSITION
TEXTURE
Felsic
Intermediate
Mafic
Pegmatitic
Granite
Pegmatite
Diorite
Pegmatite
Gabbro
Pegmatite
Phaneritic
Granite
Diorite
Gabbro
Aphanitic
Rhyolite
Andesite
Basalt
Porphyritic
Rhyolite
Andesite
Basalt
Glassy
Obsidian
Basaltic Glass
Vesicular
Pumice
Scoria
Pyroclastic
Volcanic Tuff
Ultramafic
Dunite
Color is often an indicator of the composition of a rock or mineral
and can be effectively used to identify the composition of most
igneous rocks. Light colors, including white, light gray, tan and
pink, indicate a felsic composition. Felsic compositions are rich in
silica (SiO2). Dark colors, such as black and dark brown, indicate
amafic or ultramafic composition. Mafic compositions are poor in
silica, but rich in iron (Fe) and magnesium
(Mg). Intermediate compositions have an intermediate color, often
gray or consisting of equal parts of dark and light mineral .
Beware that even though an igneous rock may have
a felsiccomposition (light color), the rock can contain dark colored
minerals. Mafic rocks may contain light colored minerals as well.
As mentioned above, the composition of most igneous rocks can
be identified using this system, formally known as the Color Index.
However, there are exceptions. The two most notable
are obsidian and dunite. Obsidian is volcanic glass which erupts as
a lava flow. Most obsidian is felsic in composition, yet typically it
will have a very dark color (dark brown to black). Dunite has
an ultramafic composition yet is apple green to yellowish green in
color. Dunite is composed almost entirely of the mineral olivine
which usually contains both iron and magnesium.
Practice Identifying Igneous Rocks
http://facweb.bhc.edu/academics/science/harwoodr/geol101/Labs/I
gneous/Igsamp01.htm
Answer at least Five
 Define
•
•
•
•
•
•
•
Magma
Lava
Extrusive Igneous Rocks
Intrusive Igneous Rocks
Streak
Moh’s Scale
The difference between a rock and mineral.
Answer at least Five
 Write
a list of at least five ways to Identify
rocks and mineral samples.
 Which has the largest crystal texture?
• Porphyritic or Pegmatitic
 What
is the name to describe an extrusive
rock’s holey outer texture on a rock such as
pumice?
 This
chart explains what Igneous Rocks are
made of and some common vocabulary words
associated with igneous rocks
Here's
something
for you to
think
about: List
the
percentag
es of
minerals
found in
rock 'Z'!"
According to the chart,
what's the maximum
number of minerals that
can occur together in
one igneous rock? Can
an igneous rock consist
of just one mineral?
What are the names of
three minerals that do
not occur together in
the same rock with
pyroxene?
 Why
use luminescent rocks in a driveway?
• Their glow lasts for 10 – 20 hrs.
1.Write the
five names of
the minerals
in Rock X.
2.Circle the
mineral that
has the
highest
percentage
in Rock X.
3. Explain
why Olivine
is at the
top of the
left side of
this chart
and Quartz
appears at
the
bottom?