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Minerals and Rocks
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Introduction:
In this lesson, students will study minerals and learn how to identify
and classify them. Minerals are rock objects that contain only one
material. |
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The activity starts with a general discussion about
how people describe objects and how scientists describe objects.
From here, students will look at a set of common classification
tests that are used to define minerals. The final activity is to
use a portion of these classification tests to identify some common
minerals.
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Minerals and Rocks: Teacher Notes:
Download:
Print
the "Which is Which? Identifying Minerals" activity.
Print
the "Examining and Classifying Minerals" chart.
Printable Examining and Classifying Minerals: Teachers
Notes coming soon.
Supplies (for a class of 30 students):
1. 15 mineral sample sets with test kits
2. 30 Mineral worksheets
3. 15 Mineral identification sheets
4. 30 pencils
Activity #1: Discussion -- Describing objects
Start a discussion on how you would describe an object. If the students
are having problems getting started, hold up something from the
room and ask the students to describe.
Opening questions: How would you describe an object? What kinds
of words are used to describe an object?
Help the students to see that the answers all involve using their
senses: sight, smell, taste, touch, and hearing
Follow-on question: When you describe an object what are some of
the properties of that object that you might use?
Possible Answers: Color, shape, size, weight, smell, taste, texture,
or the sound it makes.
Activity #2: Visual Description of Minerals
Now that the students have some understanding of how we classify
and describe objects, it is time they try and apply this to mineral
samples. This lab works best if the students work in teams of 2-4.
Give each team a mineral set. Each student should be given her own
Examining and Classifying Minerals Worksheet. Start the identification
process by having each student fill in the description column for
each mineral in his/her set. They may use the magnifying glass included
in the kit to assist in their observations.
Activity #3: Luster
Another visual property of minerals is their luster. Luster is a
way of describing the shininess of a material. It is the intensity
of quality of the light reflected by an objects surface. There are
two basic types of luster: metallic and nonmetallic. Materials with
a metallic luster shine like a polished metal surface. They are
usually dark in color and are always opaque. Nonmetallic luster
can be described by words such as glassy, brilliant, pearly, silky,
greasy, or dull. Ask the students to think of some everyday objects
that have the following types of luster?
Metallic: nail, chain, toaster
Nonmetallic: drinking glass (glassy
luster), chalk (dull luster), graphite (greasy luster), nylon (silky
luster) Using their mineral sets, the students should now identify
the type of luster for each of their samples and record their
observations on their worksheet.
Activity #4: Physical Properties -- Hardness
Descriptions are just one way we can identify rocks. It is useful
for separating minerals that look or feel quite different from
each other. But, how can we identify minerals that look quite
similar to each other? In these cases, scientists use physical
properties such as hardness and reactivity to other materials
to discern differences in the materials.
One physical test that scientists use to classify minerals is
the hardness or scratch test. This test determines a mineral's
resistance to scratching. The Mohs' Scale of Hardness, named after
the German mineralogist who developed it, Friedrich Mohs, is used
to rank the hardness of a mineral on a scale of 1 (the softest)
to 10 (the hardest). This ranking is made based on the relative
hardness of a mineral, that is, the hardness of a mineral compared
with that of other minerals. In the next activity, we will determine
each mineral's hardness by proving the scratch test. The procedure
for the hardness test is given below.
- Using the back of the worksheet, examine each specimen for
hardness. Check to see if the mineral is scratched by a fingernail,
a penny (the copper strip included in the kit will work), or
a nail (inside the kit).
- Check if the specimen scratches the glass included in their
kit.
- Using the given scale, determine the hardness number of the
mineral and record it in the last column.
- Copy the hardness number in the appropriate column on the
front of the worksheet.
Activity #5: Physical Properties
-- Streak test for color
Sometimes the true color of a mineral is not obvious by looking
at a specimen. Minerals are subject the weathering. This can change
the surface color of the material. Scientists use the streak test
to determine the true color of a specimen.
To do a streak test, drag the specimen across the white streak plate.
Vary the amount of pressure until you obtain a good streak. Be sure
to lay the streak plate flat on a table when performing the streak
test. Do not hold the plate in your hand -- it could break.
Have each student (or team) test the colors of the streaks for each
mineral and record them on the worksheet. Be careful with number
4, it will crumble if pressed too hard.
Activity #6: Physical Properties -- Acid test
In the final physical test the students will observe the effects
of an acid (vinegar) on each mineral. When moisture in the atmosphere
combines with airborne oxides of sulfur and nitrogen, sulfuric
and nitric acids are formed. These two chemicals -- known as acid
rain --have been proven to cause the deterioration of buildings,
statues, and monuments that are constructed of, or have exterior
surfaces made from, certain kinds of rocks and minerals. Geologists
use this acid test to confirm the presence of calcium carbonate
in rocks. Calcium carbonate reacts with the acid to form carbon
dioxide gas. The gas is evident in the form of bubbles or fizzing
when drops of vinegar are placed on a mineral sample containing
calcium carbonate. In this activity, one of the samples will dissolve
since it is soluble in the water contained in vinegar.
Procedure:
- Use a nail to scratch a small amount of powder onto a glass
plate. Place a drop of vinegar onto the plate and observe any
reaction with a magnifying glass.
- If the sample is too hard to scratch, drop the vinegar directly
onto the sample. Be sure to wipe off any vinegar on these specimens
after the test.
- Record your observations on the worksheet.
Activity #7: Identification
Hand out a copy of the Mineral Data sheets. Can the students identify
each mineral in their kit using the results of all of the tests?
Discuss. The answers are given in the instructor’s notebook.
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