Download Grade: 3rd Activity #: 1 Activity Title: Studying Rocks and Minerals

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Activity #:
Activity Title:
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Special Notes:
3rd
1
Studying Rocks and Minerals
Groups of 2-3
This is a wet experiment and should
ideally be done in the Science Lab
Purpose
Students will learn the difference between rocks and minerals. They will learn
some of the ways of identifying minerals. They will learn the different types of
rocks and learn what the Rock Cycle is. Students will test hardness, magnetic test,
perform streak test and acid test on several mineral samples. They will also taste
salt samples.
Equipment (An asterisks (*) indicates that an item is provided in the Learning Lab.)
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Rock samples*
Vinegar*
Magnets*
Steel nail*
Copper penny (before 1981)
Rock salt *
Glass plate*
Crushed chalk*
Droppers*
Instructions
1. Write the name of your rock/mineral specimen. Describe your rock samples.
Write your answers on Table 1.
2. Run magnets along your rock samples. Are your samples magnetic? Write Yes
or No in Table 1.
3. Test the hardness of your mineral specimen by conducting a scratch test. Use
the following objects: your fingernail, a copper penny, a steel nail, and a glass
plate. Write Yes or No in the boxes in Table 2. Write the Mohs scale number
in the last column.
4. Streak Test: Predict what color streak each of the mineral specimens will leave.
Then test your specimens on the streak plates. Write your observations on
Table 3. Some colors you will observe are greenish black, gray, white and
colorless.
5. Acid test: Perform the acid test. Place one to two drops of vinegar on your
mineral specimens and record what happens. Possible observations will include
no reaction, bubbles formed, and dissolved. Then perform a test on the crushed
chalk sample. Record your observations in Table 4.
6. Taste the rock salt samples. DO NOT TASTE THE OTHER SAMPLES!
Suggested Discussion Topics
WHAT IS THE DIFFERENCE BETWEEN A ROCK AND A MINERAL?
A Rock is made up of one or more minerals. There are 3 types of rocks. They are
Igneous Rocks, Sedimentary Rocks, and Metamorphic Rocks. We’ll discuss
these more later.
A mineral is a naturally occurring, inorganic, solid which possesses a characteristic
internal atomic structure and a definite chemical composition.
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Minerals must occur naturally. This means man-made substances such as
steel would not be considered to be minerals.
Inorganic substances are those substances that are not living and are not
formed by living processes.
Minerals will have definite chemical compositions, but these compositions
may vary within given limits.
Minerals will have distinctive physical properties such as color, cleavage,
luster, streak, etc.
MINERALS: How do we identify a mineral?
• Color - The color of a mineral is the first thing most people notice. But it can
also be the least useful in identifying a mineral. Most minerals occur in more
than one color. The other properties, such as hardness, cleavage, and luster,
must be used instead. For some minerals, color can be characteristic and serve
as a means of identification. Malichite is always green, azurite is always blue,
and rhondonite is always red or pink.
• Streak - The streak of a mineral is the color of the powder left on a streak
plate (piece of unglazed porcelain) when the mineral is scraped across it. The
streak plate has a hardness of glass, so minerals with a Mohs Hardness >7 will
scratch the streak plate and won't powder the mineral. Streak can be useful
for identifying metallic and earthy minerals. Nonmetallic minerals usually give a
white streak because they are very light-colored. Other minerals may have very
distinctive streaks; hematite, for example, always gives a reddish brown streak.
• Luster - Luster refers to how light is reflected from the surface of a mineral.
The two main types of luster are metallic (like a quarter, silvery) and
nonmetallic (like a dollar bill).
• Cleavage - The ability of a mineral to break along preferred planes. Certain
planes of weakness exist in some minerals because of their particular atomic
structure. Atomic bonds may be weaker in some directions than in others, so the
mineral will tend to break, or cleave, in that direction. Minerals may have
cleavage in only one direction, in only two directions, or in three or more
directions. The cleavage angles at which these planes intersect may be
distinctive.
• Hardness - The hardness of a mineral is its ability to resist scratching.
Friedrich Mohs, a German mineralogist, developed a hardness scale over 100
years ago. The hardest mineral known, diamond, was assigned the number 10.
The Mohs Hardness Scale ranks the order of hardness of minerals and some
common objects. For example, your fingernail can scratch the minerals talc and
gypsum, with a hardness of 2 or lower. A copper penny can scratch calcite,
gypsum, and talc. A common misunderstanding of how to identify a diamond is
that it will scratch glass. While this is true, other minerals can scratch glass,
too, as long as they have a hardness >6.
HARDNESS SCALE INDEX MINERAL COMMON OBJECTS
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Talc
2
Gypsum
3
Calcite
4
Fluorite
5
Apatite
6
Orthoclase
7
Quartz
8
Topaz
9
Corundum
10
Diamond
Fingernail
Copper Penny
Glass
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Light/Heat - There are several ways that minerals can emit light. Some of
these ways involve special lamps that emit non-visible ultraviolet light (at
least not visible to humans). The light from these ultraviolet lamps reacts
with the chemicals of a mineral and causes the mineral to glow; this is called
fluorescence. If the mineral continues to glow after the light has been
removed, this is called phosphorescence. Some minerals will glow when
heated; this is called thermo-luminescence.
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Smell - Some minerals do have odors! Generally the odor is not strong. The
smelliest mineral is sulfur. Odor is a fairly uncommon property in minerals
and not reliable in general.
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Touch - Minerals that have a distinctive feel are generally low in hardness,
but not always. Several metallic minerals such as copper have a jagged feel
due to minute, sharp protrusions. Minerals such as graphite, talc and
several other clay minerals have a greasy or oily feel. At times feel can
distinguish two minerals.
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Solubility (water and acid) - Minerals do dissolve. Pure water can dissolve
any mineral, at least partially. However most minerals do not dissolve in
water fast enough that we can detect in a short period of time. The ones
that do dissolve rapidly are therefore considered soluble and this can be
diagnostic. Solubility is not just limited to water. Many acids are capable of
dissolving minerals where water has no effect. Of course, identification of
minerals using solubility is a test that could destroy the specimen, if it is
soluble. An unneeded fragment can be used for such tests.
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Inclusions in Minerals - Many minerals have crystals of other minerals, air,
water, tar, petroleum, rocks and in the case of amber, even animals included
in their interiors. They are called, appropriately enough, inclusions.
ROCKS
Rocks are the most common material on Earth. They are naturally occurring
combinations of one or more minerals.
There are three main classes of Rocks. They are classified according to how they
originated.
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Igneous rocks form from cooling bodies of magma. Magma is the term for
liquid or melted rock and is usually quite hot. When magma flows onto the
surface of the Earth from a volcano, it is called lava. When the lava cools
and forms a rock, that rock is an igneous rock. But there are also rocks that
form from magma that does not reach the surface of the Earth. These two
types of igneous rocks are called extrusive or volcanic (because it extruded
or came out of the Earth in a volcano) and intrusive or plutonic (because it
intruded and stayed inside the Earth).
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Sedimentary rocks are formed by the accumulation and subsequent reformation of sediments (broken down pieces of all 3 kinds of rocks caused
by weathering, erosion and/or chemical breakdown). Water is always a key
component in sedimentary rocks. Where there is water, there are
sedimentary rocks being formed? Another common factor to sedimentary
rocks is that they originate on the surface of the Earth, unlike most igneous
and metamorphic rocks which originate in the interior of the Earth's crust.
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Metamorphic rocks are formed from older "parent" rock (either igneous or
sedimentary) under intense heat and/or pressure at considerable depths
beneath the earth's surface.
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Primordial rocks (minor class of rocks) are those that initially formed in
outer space as the solar system (sun and planets) formed. These objects
became comets, asteroids, meteoroids, and ultimately the planets. When
they broke apart and hit the Earth, they became Primordial rocks.
ROCK CYCLE
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Over time, various weathering processes erode igneous rocks and these
rocks and the resulting particles or chemicals settle into beds and are
compressed and cemented into sedimentary rocks. If these rocks are
buried, heated and highly compressed they will be made into metamorphic
rocks. If these rocks continue to be heated and compressed to the point
that they melt, then the molten rock might eventually form another igneous
rock. This is called the Rock Cycle.
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The rock cycle is an illustration that is used to explain how the three rock
types are related to each other and how Earth processes change a rock from
one type to another through geologic time. Plate tectonic movement is
responsible for the recycling of rock materials and is the driving force of
the rock cycle. It forms a complete circle as one rock can be turned into
another.
HOW DO WE USE ROCKS AND MINERALS?
Everything we do involves rocks and minerals and the metals we extract from them.
It is estimated that you - and every other person in the United States - will use
more than a million pounds of rocks, minerals and metals during your lifetime
including:
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lead - used in the construction of batteries, as a radiation shielding during
x-ray treatment by your doctor and dentist and as a protective shield on
your TV screen to protect you from radiation.
zinc - used as a rust inhibitor for steel in cars, buildings, bridges, ships and
trains.
copper - used in the manufacture of copper wire to conduct electricity
needed in your car, home, office, school, church, appliances.
aluminum - Cans, aircraft and automobile construction, sporting and
electronic equipment, appliances.
iron - Used to make steel for cars, subways, ships, cans, building
construction, heavy equipment, appliances and towers.
clays - Used to coat the pages of newspapers, magazines, stationery,
brochures and boxes so that the ink used in printing on them will be bright
and will not run. Also used as a brightener and abrasive in toothpaste and to
provide a smooth coating for your stomach in medicines.
salt - Used in food preservation (almost all canned and frozen food contain
salt), to enhance the taste of foods, and to melt the ice on streets and
during the winter.
stone, sand, gravel and cement - Use in streets, highways and sidewalks; in
the foundation for your house and school; as decorative materials for yards
and gardens; in water purification plants to protect your health and in the
construction of buildings from the smallest homes to the tallest buildings
Minerals in Your Bedroom
Hematite: hinges, handles, mattress springs
Chromite: chrome plating on bed
Quartz : mirror
Graphite, Galena, Sphalerite : Batteries
Brass (an alloy of copper and zinc): base of lamp
Quartz: light bulb
Wolframite: lamp filament
Copper: lamp wiring
Minerals in your bathroom
Fluorite: toothpaste
Gold: fillings,
Cinnabar: fillings
Feldspar: porcelain toilet
Chromite: plumbing fixtures,
Copper: tubing on toilet
Borax: abrasive, cleaner, and antiseptic
Minerals in your kitchen
Quartz: drinking glasses
Hematite, Chromite, Galena, Copper, Quartz: Dishwasher
Hematite , Chromite: stainless steel
Galena, Copper, Cinnabar: thermometer
Pentlandite: - Fridge
Halite: table salt
Additional Resources
http://galleries.com/minerals/physical.htm
http://www.mineralogy4kids.org/
Rock Experiment Lab Sheet
Name________________________
Date_____________
Table 1. Sample Description
Specimen # and Name
Description
Magnetic
Table 2. Scratch Test/Hardness Test Results
Specimen
Fingernail
is scratched by
Penny
Scratches
glass
nail
Mohs Scale
number
Mohs Scale of Hardness
Mohs Scale
Number
1
2
3
4
5
6
7
8
9
10
Common Tests
Scratched by fingernail
Scratched by copper penny
Scratched by steel nail
Scratches glass
Scratches all common materials
Table 3. Streak Test Results
Specimen
Predictions
Observations
Table 4. Acid Test Results
Specimen
Predictions
Observations