Mini Encyclopedia ROCKS

ENCYCLOPEDIA

Explore the world of rocks

NORAZILA

Written by
Sarah Phillips.
Designed by

Tracy Hare.

With thanks to Kevin Walsh,
Lauren Mitton,

Graham Kennedy,
and Scoot.

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NORAZILA

Igneous rocks 4
Igneous rocks to spot
Sedimentary rocks 6
Sedimentary rocks to spot
Metamorphic rocks 8
Metamorphic rocks to spot
10
c minerals 12
s to spot 14
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20
22

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Granite

Igneous rocks are usually hard.
They form when molten magma cools.

4

imentary rocks form when layers
sand or mud are dried and
rushed together. Gradually, they

form a new layer of rock.

Sandstone

Metamorphic rocks
form when existing
rocks are heated
and squeezed. -

Marble

Minerals are made up of different elements. Some
minerals, such as gold, contain only one element
but in most, two or more elements combine. If
you look closely at some rocks, you can see the

different minerals they contain.

Feldspar Biotite Quartz

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ICJneous rocks

Igneous rocks form when molten

agma cools. The type of rock

n the makeup of the
speed of the
gma

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The magma ------::::iP :;,~-~.

pushes between
other rocks.

..f• Extrusive
igneous rocks
. . form when the
: · · ,; •• . magma flows
·~ · or is hurled out

• of volcanoes.
Magma that flows

( out of a volcano
is called lava. It
cools quickly.

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'agmtl.._

e surfa

Red-h
magm

19neous roeks__... to
spot

~ -........J

Granite is made of quartz, Peridotite is heavy, with
feldspar, and mica. coarse grains.

• In amygdaloidal basalt, minerals
have formed in the air bubbles
Pegmatite has large crystals that were left as the basalt cooled.
of feldspar, quartz, and mica.

Dolerite is very common. It has Serpentine is fine-grained. It
medium-sized grains. contains quartz and feldspar.

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Extrusive igneous rocks !

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Agglomerate is made up Obsidian has a smooth
of rounded lumps of other surface. It splinters easily,
igneous rocks.
forming sharp edges.

Pumice is full of gas bubbles Basalt is the most common lava
and is very light. It will float rock. It forms when lava cools
on water. quickly and is fine-grained.

. Q , ...

Rhyolite is fine-grained. It Tuff is formed from hardened
contains quartz and feldspar. volcanic ash.

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!Q

SedimentarlJ rocks

Fossils are the remains
of things that lived in earlier
times. Fossils are found mainly
in sedimentary rocks.
The river wears away the floor of
the valley and carries sedime·nt
towards the sea.

!

Streams wear away the Wind and rain break 'I
rock. When hard rock off tiny fragments of
stops the water from I
wearing away a deeper rock, smoothing and
channel, a waterfall forms. "weathering" it. These I
fragments of rock are
known as sediment.

The tumbling water
breaks the rock down
to form sand or mud.

sptoot

elastic sedimentary rocks are made
up of small pieces of other rocks.

Breccia is made up of angular Mudstone is made up of
pieces of other rock. hardened grains of mud.

Sandstone forms when Conglomerate contains rounded
grains of sand become pebbles of other rock that have
cemented together. become cemented together.

Shale is similar to mudstone Clay has fine grains. It can be
but breaks into thin sheets. soft when wet.

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Chemical sedimentary Biogenic sedimentary
rocks form when an area
of water evaporates and rocks are made up of
leaves behind salt and shells and the other
other minerals. remains of living
things.

Rock salt can be a range of Limestone is made
different colors depending from calcite.
on the impurities it contains.

J lit

: I 1t1

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Stalactites form over Chalk is a very pure,
thousands of years from the white limestone.
minerals in dripping water.

Flint is made of the mineral Coal forms from squashed
quartz. It is very hard. layers of plant material.

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Metamorphic rocks
--J

Metamorphic rocks are rocks that have
been "changed." They form when igneous
or sedimentary rocks are heated,
crushed, or deeply buried. They are
often harder than the original rock.

Volcanic heat

As lava forces its way through the Earth's crust,
it heats and crushes the rocks nearby. The heat and
the pressure change the whole makeup of the rock.

.!

I,I'

I

onic plates

The Earth's crust is
broken into sections
called tectonic plates.
These move very slowly, carried by the
rock beneath them. When tectonic plates
move towards each other, they squash
layers of rock.

Meteorite crater

When meteorites
hit the Earth,
they melt or
shatter the rock
where they land.

Metamorphic rocks to -.,

spot

Steatite is known as soapstone. Eclogite is formed at very high
It is soft and slippery to touch. temperatures deep in the Earth.

Marble forms when limestone Gneiss has wavy bands of
is heated or squashed. feldspar, mica, and quartz.

~uartzite forms when sandstone Hornfels forms when
1s heated or squashed. mudstone or shale is heated.

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Schist forms when Amphibolite is dark in color,
mudstone and shale is
heated and squashed. with small flakes of black
and white.

Migmatite is made of granite Slate forms when mudstone or
and gneiss. shale is heated or squashed.

Spotted slate splits into thin Mylonite is formed by
sheets. Its spots are all made stretching rock.
of one mineral.
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t:z
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Rock minerals

Minerals are the building blocks that make

up rocks. There are more than 4,000

different minerals. We can identify them in
many ways, including their color, the way

they break, how they reflect light, and

how hard they are. Nearly all minerals
come in hard blocks
Crystals have flat called crystals.
faces. Quartz crystals
have six flat sides and
end in a pyramid.

Most crystals \
have a regular ....

shape. -

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We can identify • Talc 1
minerals by their Gypsum 2
hardness. Moh's Calcite
scale of hardness Fluorite 3
grades minerals Apatite 4
from 1 to 10. Feldspar 5
A mineral with
a higher grade 6I
scratches those
with a lower I
grade. Talc is the
softest mineral 19
and is 1, diamond
is the hardest and
is 10.

Quartz

Purple l· 1- Topaz
Amethyst , Corundum
Quartz
,-

~·. '·

Diamond

Rock mi Stpoot

Gypsum forms when salty water Hornblende is commonly
evaporates. It is used to make a found in igneous and
metamorphic rocks.
plaster when you break a leg.

Garnet is a metamorphic Olivine is usually a green color.
mineral. It is not a common mineral.

Calcite is colorless or white. Feldspar is found in
~ - 20 igneous, metamorphic,
and sedimentary rocks.

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Quartz is very common . Mica is a mineral that glitters.
There are several different
types of quartz. Light is reflected from its flat
surfaces.

Augite is mainly found in Agate has very fine grains. I
igneous rocks. It is often a bright color.
I

Staurolite is a reddish- Kyanite is a deep blue
brown color. color. It has long,

column-shaped crystals. 21

Gemstones --

Gemstones are crystals Rough diamonds
that are especially look like pebbles
beautiful and valuable. of cloudy glass.
People cut and polish
them to improve their
color or shine and often
set them in jewelry.

Marci diamonds

Diamond When a diamond is
set in a ring cut and polished, it
sparkles and shines.

Diamonds are the
hardest natural material.
50 only a diamond can cut

another diamond.

aquamartn
me mineral,

ng colo

rttles.

tall ge
ecom

animals. FOr
pearls form insid

a shells.

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Garnet Amethyst Aquamarine

AUCJUst

Ruby Peridot Sapphire

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Gemstones have been chosen for each I•

month of the year. Your birthstone is the I
gemstone for the month in which you
were born. I

Diamond Emerald Pearl

November

Opal Citrine Turquoise

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