Name
Period
Date
CHAPTER 3 CHAPTER INVESTIGATION A
Rock Classification
Targets:
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Know the three types of rocks, how they are formed, and the characteristics unique to each type of rock
Use scientific test and a dichotomous key to identify rocks and minerals
Using deductive reasoning, classify and identify rocks using a dichotomous key
OVERVIEW & PURPOSE
In this activity, you will:
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
Look at rock samples and a key that will help you classify them.
Classify the rock samples. The rocks are igneous, sedimentary, or metamorphic.
QUESTION:______________________________________________________________________
MATERIALS
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hand lens, 6-8 rock samples, and Rock Classification Key data sheet
HYPOTHESIS:____________________________________________________________________
________________________________________________________________________________.
PROCEDURE
Check off each step as you do it
1. Choose a rock sample.
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Get a numbered rock sample.
Record its number in the data table.
2. Look carefully at the rock sample.
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Look at the sample with your eyes alone.
Examine the sample with the hand lens.
Write what you observed in the data table under "Description of Visible Properties. "
3. Classify the rock sample.
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Look at the Rock Classification Key. Each step of the key has two statements.
Start with Step 1 of the key. Choose the statement that best describes your rock sample.
Look at the end of the statement. Go to the step number it shows.
4. Classify the rock sample.
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Look at the next pair of statements. Examine the rock sample.
Choose the statement that best describes your sample.
Go to the next step number it shows.
Work through the key. Your choices should lead you to a classification that fits your rock.
5. Repeat Steps 2-5 for each rock sample.
6. Use the data table below to record your data.
Data Table
Sample #
Description of Visible Properties
(Ex: 1, 2, 3, etc.) (Ex: color, weight, minerals, layers, shiny, crystals, etc)
Rock Type
(Igneous, Sedimentary,
Metamorphic)
*BONUS*
Rock Name
OBSERVE AND ANALYZE
1. Interpret Use the Rock Classification Key and the information in the table to find the rock type. Write the
type of each rock in the "Rock Type" column.
2. Identify Limits Did you have problems using the key? If so, what were they?
Which samples did not fit easily into a category?
How could you improve the key?
CONCLUDE
1. Compare and Contrast How are igneous and metamorphic rocks alike?
How can you tell igneous and metamorphic rocks apart?
2. Analyze Examine a sedimentary rock sample in which you can see particles that are held together. In
addition to sight, what other sense could help you classify the rock?
3. Apply Think about what you learned from this lab that would help you make a classification key that
someone else could use. How would you make a key to classify a collection of music CDs?
Write the first pair of statements that would start your music CD classification key. Use the Rock Classification
Key as a model.
Key to Rock Classification
1.
Look at the composition of your rock. Is the rock made up of visible particles? (for example,
mineral crystals or sand)
YES………………………… go to 3
2.
Look at the texture of your rock. Is the rock glassy or porous (sponge-like)?
YES………The rock is IGNEOUS.
3.
NO………………………….. go to 5
Determine the type of particles that make up your rock. Is the rock made up of individual particles
(sand or pebbles) that are cemented together?
YES………The rock is SEDIMENTARY.
4.
NO………………………….. go to 2
NO………………………… go to 4
Determine if the mineral crystals of the rock. Do the rocks mineral crystals tend to line up or form
bands (foliation)?
YES………The rock is METAMORPHIC. NO………………………… go to 7.
5.
Determine if the rock is made up of layers. Does the rock have layers or break into layers?
YES………… go to step 6
6.
NO………………The rock is IGNEOUS.
Is the rock shiny?
YES………The rock is METAMORPHIC. NO………………The rock is SEDIMENTARY.
7.
Look at the mineral crystals. Is the rock made up of two or more types of mineral crystals?
YES………The rock is IGNEOUS.
NO………………The rock is METAMORPHIC.
Key to Rock Identity
1.
Is the rock composed of layers? (A magnifying glass may be needed to determine whether the
rock has layers or not.)
YES………………………… go to 3
2.
Are there visible crystals in the rock?
YES………………………… go to 4
3.
NO………………………….. go to 9
Does the rock easily split into thin, flat pieces?
YES………………The rock is SLATE.
10.
NO………………The rock is LIMESTONE.
Does the rock have visible crystals?
YES………………The rock is GNEISS.
9.
NO………………………….. go to 7
Is the rock dark gray to black?
YES………………The rock is BASALT.
8.
NO…………………………. go to 6
Is the rock very lightweight, with holes?
YES……………The rock is PUMICE.
7.
NO………………………… go to 10.
Does the rock look like black glass?
YES………… The rock is OBSIDIAN.
6.
NO………………………… go to 8
Is the rock mostly white, possibly with streaks of color?
YES…………… The rock is MARBLE.
5.
NO………………………….. go to 5
Can sand be scraped off of the rock?
YES…………. The rock is SANSTONE.
4.
NO………………………….. go to 2
Is the rock very lightweight, with holes?
YES……………The rock is PUMICE.
NO……………………The rock is SHALE.
NO …………………The rock is GRANITE.
ANSWER KEY
Observe and Analyze
1. Students must correctly classify the rock samples as igneous, sedimentary, or metamorphic using the
classification key.
Sample data: 1, mineral crystals and speckled, igneous; 2, sea fossils, sedimentary; 3, wavy bands and shiny,
metamorphic
2. Students could have experienced some difficulty in matching the characteristics of their samples exactly to
the descriptions in the key. Samples that did not fit easily into a category will vary depending on the samples
used.
Accept all reasonable suggestions for improving the key.
Conclude
1. Igneous and metamorphic rocks are similar in that they are both made of mineral crystals that fit tightly
together and may be large enough to see without magnification.
The minerals in metamorphic rocks tend to be lined up in bands or layers, or metamorphic rocks tend to be
shiny.
2. Touch could help identify a sedimentary rock made of relatively large particles.
3. Answers will vary from student to student.
A key for a music collection might start with questions such as what type of music it is, when it was recorded,
or who the recording artist is.
TEACHER NOTES
Lab Preparation
 Copy and distribute the Rock Classification Key to each group of students. Review how to use it.
 You might increase the number of rock samples to ten, if possible. Do not use slate (too similar to shale)
or limestone (can be difficult to identify without testing with hydrochloric acid).
 Prior to the investigation, have students read through the investigation and prepare their data tables. Or
you may wish to copy and distribute datasheets and rubrics.
UNIT RESOURCE BOOK, pp. 196-205
SCIENCE TOOLKIT, F15
Lab Management
INCLUSION Encourage students with vision impairments to handle the rock samples to feel their textures.
 Remind students that visual properties include size of particles or mineral
 If students do not understand how to use the classification key, demonstrate the process with one rock
sample.
Knowledge Targets:
· Know what a dichotomous key is and its purpose
· Know the three types of rocks, how they are formed, and the characteristics unique to each type of rock
· Know the rock cycle and how the three forms of rock can change into each other
· Know that minerals are the building blocks of rocks, have unique properties, and are valuable resources
· Know the difference between chemical and mechanical weathering
· Erosion shapes the earth by water, wind, and ice
Add Skills Targets
Skills Targets:
· Use scientific tests to identify rocks and minerals
· Demonstrate an understanding of how rocks an minerals are used in real life situations
Add Reasoning Targets
Reasoning Targets:
· Using deductive reasoning, classify and identify rocks using a dichotomous key
· Connect the purpose of rocks and minerals with their characteristics
· Make a connection about the relationship between rocks and minerals and understand how different combinations of each determine
the different type of rock formed
· Investigate and research examples where natural forces on or within the earth are changing or have changed rocks through the rock
cycle. Identify these natural forces and explain their roles in the rock cycle.