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Investigating
Rocks and Minerals
In Your World
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Rocks
are all around us. You can see rocks inside
your house, in your yard, on your street, on a country road, everywhere
you look. Statues, chalk, marble, pencil
lead, sandpaper, glass, tombstones, bricks, the walls of your room, mountains,
pebbles, soil, a volcano are all rocks!! Rocks are used to build homes,
an aluminum baseball bat, a washing machine, video games, airplanes, cars,
and jewelry! Rocks aren't always solid. Sand and Mud are rocks. No matter
where you are you are always close to rocks and minerals. They are fascinating
and exciting so let's begin our investigation to learn more.
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We'll
begin with a look at the structure
of the earth because that is where all rocks come from.
They have been on Earth for almost 4 billion years. Geologists record
time with the Geologic Time Table.
 The
Earth has 3 layers: the crust, the mantle and the
core (which is subdivided into
the outer and inner core.) Each layer is unique and
you can find the interesting details of the layers at:
Learning About
the Structure of the Earth
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How
do we classify rocks?
There are 3 main types of rocks depending on how they were formed
in the different layers of the Earth.
They are: Igneous, Sedimentary, and Metamorphic.
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Type
of Rock
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How
it is Formed
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Where
it is Formed
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Other Facts& Examples
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rock
weathered to many pieces
of rock and soil which then settles into layers. The layers are
squeezed together until they harden into rock.
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where
oceans, lakes, or other bodies of water exist or existed
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layered,
soft often containing fossils.
limestone, chalk, coal, sandstone, shale
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rock
formed when melted rock cools and hardens
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lava
from volcanoes or magma that cools inside the Earth
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often
shiny or glossy. basalt, granite, pumice, quartz, obsidian
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igneous,
sedimentary, or other metamorphic rock that is changed by heat
and pressure deep within the earth.
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deep
within the Earth
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hard,
often contains crystals, may have bands or layers marble, slate,
gneiss, schist
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The
heads at Mt.  Rushmore
are carved out of an igneous rock called granite
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The heat of lightning striking the sand of a beach can melt the sand
to form a glassy rock called "fulgurite."
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A rock can begin as one type and can
change many times. In fact, rocks are always changing. However, the
changes happen so slowly that they are difficult to see. We have seen
above that heat and pressure can change rocks which then break down
by weathering and move by erosion.
It can take thousands of years for rocks to weather and erode. This
process of changing is called the rock
cycle.
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Weathering
is the process that breaks rocks down into smaller pieces. Weathering
can be caused by: wind, rain, ice, running water, plant roots, chemicals,
freezing and thawing.
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Erosion
is the movement of rock pieces from place to place. Erosion can be caused
by: wind, rain, running water, waves, gravity, and moving ice.
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What
else do we know about rocks?
A rock is a material made of one or more minerals.
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What is a Mineral?
Minerals
are made from 92 elements that join together
in many different ways. Some minerals are made of only one element,
such as silver. Most are a combination of two or more elements, such
as granite which is made of quartz, feldspar, mica. Scientists have
identified over 3,000 minerals. The
particles of minerals are arranged in a repeating pattern called a
crystal.
Recognizing
a mineral is not an easy job. There are several different properties
of minerals and tests that are used to identify them. The properties
are: luster, hardness,
color, streak, cleavage, crystal shape, and magnetism. Challenge yourself
to identify
minerals.
Mineral names and uses
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The
blue color is the mineral "azurite." The green color is
"malachite." |
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Diamond is
the hardest mineral.
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Meteorites, rocks
from space, help scientists learn about the solar system.
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This
is just the exciting beginning of your investigation. At Links
for Rock Hounds meet Rocky and Rex, solve mysteries, be
inspired by beautiful photos of rocks and minerals, and discover
more as you learn how to think like a geologist
and mineralogist.
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