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Minerals and Rocks
Based on Discover God’s Creation
Chapter 8-1, 2 & 3
By Rebecca K. Fraker
Matter
• Matter is anything is anything—solid,
liquid, or gas—that has mass and takes up
space.
• Matter on earth is made up of one or more
of the 92 naturally occurring atoms or
elements, substances that normally do not
change into other substances.
Elements
• Each element has special properties that
identify it.
• While elements do not change, they can
combine with others to form compounds.
• When hydrogen and oxygen combine they
form a common compound –water.
Other examples of compounds:
Minerals
• Minerals are elements or compounds that
occur in Earth.
• Gold, silver, and copper are singleelement minerals.
Minerals
• Most minerals, however, are compounds
made up of two or more elements.
• Table salt is made of sodium and chlorine.
plus
salt
Sodium
Chlorine
All minerals share four features:
• They occur naturally in the environment.
• The do not come from living things.
• Each has unique properties and
composition.
• Their atoms are arranged in an orderly
pattern.
How are minerals found?
• Minerals are often found in concentrated
deposits.
• Some minerals, such as quartz and
feldspar, form as magma cools in the
cavities or cracks in the crust.
• Heavy minerals, such as gold, are
deposited as water washes them into
rivers and they settle to the bottom.
Other Minerals
• Still other minerals, such as gypsum and
halite (rock salt) form as the water they are
dissolved in evaporates from shallow
lakes.
Identifying Minerals
• How do you tell the difference between
fool’s gold and real gold?
• Geologists use several tests to identify the
properties of minerals.
Hardness Test
• The Mohs’ scale indicates the hardness of
a mineral. It is based on 10 minerals.
Number 1 is the softest, and Number 10 is
the hardest.
• A mineral is tested by seeing which other
minerals it will scratch. If it scratches
1,2,and 3, it has a hardness of 4.
• Diamond has a hardness of 10 and can
scratch all other minerals.
Mohs’ Scale
• An easy way to test hardness is to use your
fingernail, a penny, a knife blade, and glass.
Fingernail=1 Copper penny=3
Knife blade=6 Glass=8
Streak Test
• Some minerals are identified by their color.
• Sulfur, for example, is bright yellow.
• When the color of a mineral is hidden by dirt,
you can do a streak test by rubbing the
mineral across a rough piece of tile or a metal
file.
• The color of the streak helps identify it.
• Fool’s gold leaves a dark-green streak.
• Real gold leaves a golden streak.
Luster Test
• Luster refers to how a mineral reflects
light.
• A mineral can have a metallic or
nonmetallic luster.
• Galena, which shines like a piece of metal,
has a metallic luster.
• Quartz has a nonmetallic luster because ti
is glassy, waxy, or dull in appearance.
Crystal-Shape test
• The crystals of each mineral have a
specific shape.
• Salt crystals are always shaped like a
cube.
• If you can see the shape of a crystal, you
can identify the mineral. But that is not
always easy.
Salt
Crystals
sulfur
feldspar
amythest
Cleavage/Fracture Test
• If a mineral is hit hard enough, it will break
or fracture.
• Some minerals, like fool’s gold, break
unevenly.
• Others, such as mica, split into thin
sheets. This quality is called cleavage.
Other tests
• A few minerals contain iron and are
attracted by a magnet.
• Some minerals contain carbonates that
bubble and fizz when acid touches them.
• Rock salt (halite) can be identified by its
taste, while sulfur when scratched gives
off a rotten eggs smell.
Other tests
• Calcite splits light into two beams that form
a double image.
• Some minerals are fluorescent. They
normally look dull, but are bright and
colorful under ultraviolet light.
Metals
• Minerals such as gold, copper, and
aluminum are metals
• They have luster and can be hammered
into flat sheets or drawn into a wire.
• Metals are good conductors of heat and
electricity. Because of these qualities,
they are widely used.
Mineral or Rock?
• Minerals are single elements or
combinations of elements.
• Rocks are mixtures of various minerals.
• In mixtures, ingredients do not chemically
combine and change; they simply stick
together.
Rocks
• Concrete and granite
provide examples that
demonstrate such
mixtures.
• Rocks are often identified
by the minerals that stick
together to form them.
• Concrete is sand, cement,
and water mixed together.
It then is poured into a
shape and hardens.
Granite
• Granite is a common rock used for
buildings, monuments, and counter tops.
• Feldspar is the light-colored part of
granite, quartz makes up the clear
crystals, and biotite and mica are the darkcolored specks.